WASHINGTON — The Trump administration has embarked on its toughest round of economic sanctions against Syria, intending to break President Bashar al-Assad’s reign over the country and stop a civil war that has claimed over half a million lives.

Secretary of State Mike Pompeo says the administration will not end the pressure campaign on Mr. al-Assad and his backers until he agrees to a United Nations resolution prompting peace talks and a transition of power.

But diplomatic and humanitarian assistance experts are wary of the strategy, saying economic sanctions alone, no matter how punishing, will do little to bring Mr. al-Assad to the negotiating table and will only worsen the humanitarian crisis in Syria, which has been exacerbated by a collapsing economy.

Critics also warn that the Trump administration will waste the broadened sanctioning power Congress gave it if diplomatic outreach to the Syrian government and its allies does not accompany economic punishment.

“Sanctions alone cannot solve the problem,” said John E. Smith, the former director of the Treasury Department’s Office of Foreign Assets Control. “It’s difficult to see what else the U.S. government is doing in Syria other than putting a bunch of Syrian regime insiders on a list that they don’t really care one way or the other they are on.”

The newest round of sanctions on Syria comes as the Caesar Syria Civilian Protection Act, which President Trump signed into law in December, went into effect in mid-June.

The legislation — named after a military photographer, code-named Caesar, who leaked over 50,000 photos of torture and other atrocities taking place in Mr. al-Assad’s prisons — is stronger than previous sanctions, which started in 1979 when Washington first declared Syria a state sponsor of terrorism.

It allows the United States to freeze the assets of any person or business dealing with al-Assad’s government, regardless of nationality. It also targets Russia and Iran, Mr. al-Assad’s primary backers.

The law also punishes individuals and corporations anywhere in the world dealing with three crucial sectors of the Syrian economy: the domestic oil industry, the Syrian military and engineering or construction businesses operating in government-held regions.

“Congress is giving companies around the world a choice,” Mr. Smith said. “You can go do business in Syria if you would like, but if you do, you risk being cut off from the almighty dollar and the U.S. financial system.”

Since June, over 40 elites have been sanctioned, including Mr. al-Assad’s wife and his oldest son, other members of his extended family and senior military leaders. Business people crucial to the reconstruction of government-held Syria have also been targeted.

Experts note that sanctions have caused widespread concern in the country. Companies interested in rebuilding Syria’s cities and countryside — which could require $250 to $400 billion to reconstruct — may be scared away from doing business in the region, stalling Syria’s path to recovery.

Ahead of the United States announcing its first round of Caesar Act sanctions in mid-June, Syria devalued its currency by 44 percent.

But Trump administration officials say their efforts, billed as a “sustained campaign of economic and political pressure,” has just started, and they expect many more actions to come.

“This will continue to be the ‘summer of Caesar,’” said Joel D. Rayburn, the State Department’s special envoy for Syria. “There will be no end to them until the Syrian regime and its allies accede.”

The sanctions arrive at a time when Mr. al-Assad has nearly won Syria’s nine-year civil war, and finds his economy crumbling.

The currency is nearly worthless, making basic commodities unaffordable to large swaths of the population. Protests against poor living conditions have erupted in parts of the country. The coronavirus is also taking hold. And Syria’s main trading partner, Lebanon, is dealing with an economic meltdown that has spillover effects into its own economy.

Former government officials agree that the sanctions, piled on top of the current state of Syria’s economy, could have a devastating impact on the humanitarian situation in a country where nearly 80 percent of the people live in poverty.

Others note that Mr. Trump’s increasing reliance on sanctions against repressive governments like Iran and North Korea has done little to change behaviors of the ruling class, whose members often find ways to evade the punitive measures or pass down the punishing effects onto their citizens.

“The regime elites continue to flourish, they continue to get luxury goods, they continue to do their shopping trips,” Mr. Smith said. “It is generally the people of the jurisdiction that pay the ultimate penalty from the poverty that is inflicted on that government.”

There is little question that American sanctions, writ large, have made life harder for many ordinary Syrians.

Business and factory owners describe the headache of importing and exporting goods using channels outside the American banking system and of losing international customers and suppliers who do not want to run afoul of the sanctions.

Cheaper but inferior Syrian- and Iranian-made products have replaced other imported ones at supermarkets. Iran, struggling with its own American sanctions, cannot throw Syria a major lifeline.

But the causes of Syria’s economic crisis go far beyond the sanctions, including a civil war that has decimated its cities, factories, infrastructure and hospitals.

A shopkeeper from the al-Midan neighborhood of Damascus blamed runaway inflation and soaring food prices on corrupt dealings between the government and Assad cronies.

“The corruption and government checkpoints and looting are making our lives and our business harder than the American sanctions,” said the shopkeeper, Abu Muhammad, 60.

Democratic and Republican lawmakers have put provisions into the Caesar Act ensuring humanitarian organizations are still able to provide food and aid to Syrians.

But humanitarian workers operating in the country note that despite best intentions of lawmakers, the reality on the ground will be different.

They note medicine is already becoming harder to bring into the country. Insurance companies are telling aid organizations they will not cover certain procedures. A.T.M.’s have shut down, causing relief workers to waste precious time standing in line to withdraw salaries.

This may not all be directly because of the sanctions, aid experts said, but the vast nature of the United States’ sanctions efforts is scaring companies away from the region, even though they may be legally allowed to operate.

“It’s a double-edged sword,” said Basma Alloush, policy and advocacy adviser for the Norwegian Refugee Council, a humanitarian organization that operates in Syria. “If the U.S. is using such sweeping, vast sanctions to yield some kind of political goal, they’re not paying enough attention to the unintended consequences.”

She added: “With the U.S. adding this additional pressure on ordinary people that have gone through hell and back, they really need to do a lot more to demonstrate how exactly they’re going to be protecting these civilians.”

To hear the Syrian government tell it, American sanctions are the root of all of Syria’s economic problems. Strident propaganda to that effect fills state television and the mouths of government loyalists.

“The moment the United States of America lifts the sanctions and stops the Caesar Act, the prices of goods, commodities and foodstuffs will drop at least 50 percent,” Mohammed Samer al-Khalil, the economic minister, said at a talk on July 15.

Defiance is a common response. A government employee in Damascus, Abu Nidal, noted that Syrians had already survived punishing American sanctions from the 1980s on without succumbing to what he called “American hegemony.”

“These measures will never ever change the peoples’ loyalty and support for President Bashar al-Assad and his war against the terrorist groups and to retake every inch of Syria,” added Abu Nidal, 50, who, like most Syrians interviewed, asked to be identified by a nickname because he feared repercussions for speaking to a foreign journalist.

Mr. al-Assad’s government, like the aid groups, insists that the sanctions snarl the process of importing medicines, vaccines and medical equipment. But verifying those claims has proved difficult in a country with little transparency and an interest in vilifying the United States.

During a rare visit to Syria by New York Times journalists last year, the government did not allow them to visit a hospital or interview doctors about what officials said were medical shortages caused by the sanctions that preceded the Caesar Act.

A physician at a government hospital in Damascus, interviewed this week, however, said he had not seen any gaps recently.

“The Syrian health minister keeps saying the Caesar Act is badly affecting the health sector,” said Dr. Muhammad, 45, who asked to be identified by his first name to avoid punishment for speaking, “but I haven’t noticed it.”

Experts note a major goal for these sanctions is to restrict the flow of capital from Russia and Iran into Syria. The rationale is that if Mr. al-Assad’s primary backers feel the financial pain of sanctions, they could be persuaded into helping negotiate a peace deal.

But absent a diplomatic strategy to accompany economic sanctions, critics worry the Trump administration will not get Mr. al-Assad’s allies to change the status quo.

“As Russians will tell you, they’ve been sanctioned themselves — it’s not a game changer to them,” said Alexander Bick, who was director for Syria in President Barack Obama’s National Security Council. “Ultimately, sanctions are a tool in a diplomatic process.”

He added that any change in Syrian leadership would be “embarrassing” to Russia: “It would undermine Putin’s message — which has been, ‘I stand by my clients’ — and would undermine Russia’s broader goal to prevent America from changing regimes at will.”

Some scholars say the Caesar Act sanctions could be leverage to achieve small, specific goals, such as the release of political prisoners. Others think they could have a greater effect — with the broad jurisdiction Congress has provided the Trump administration helping to achieve peace in a region that has been plagued by a brutal civil war.

But they note that only thirteen businesses and individuals that have been sanctioned since June are actually under the new law. Most are sanctioned under executive orders signed by Mr. Trump in October 2019.

Some question why Russian individuals and entities have not been sanctioned, given their outsized role in the conflict.

“Does this fall into that huge area of uncertainty about how willing the Trump White House is to take actions against Russia?” said Steven Heydemann, a senior fellow at the Brookings Institution. “It risks calling the credibility of the administration’s commitment to the sanctions into question.”

Pranshu Verma reported from Washington, and Vivian Yee from Beirut. An employee of The New York Times contributed reporting from Damascus.