American officials, however, disputed that, saying that Mr. Macron misinterpreted the conversation. About 2,000 American troops are in Syria to fight the Islamic State, or ISIS, not to play a role in the civil war. In public comments before the chemical attack that prompted him to launch airstrikes, Mr. Trump said he wanted to pull them out right away. Advisers urged him to hold off, and he gave them five to six months to complete a withdrawal.

“The U.S. mission has not changed — the president has been clear that he wants U.S. forces to come home as quickly as possible,” Sarah Huckabee Sanders, the White House press secretary, said in a statement Sunday night. “We are determined to completely crush ISIS and create the conditions that will prevent its return. In addition, we expect our regional allies and partners to take greater responsibility both militarily and financially for securing the region.”

The new American sanctions were announced on Sunday by Nikki R. Haley, the ambassador to the United Nations and the administration’s leading public voice excoriating Russia in recent days. “They will go directly to any sort of companies that were dealing with equipment related to Assad and chemical weapons use,” she said on “Face the Nation” on CBS. “And so I think everyone is going to feel it at this point. I think everyone knows that we sent a strong message, and our hope is that they listen to it.”

Mr. Trump has tried through most of his presidency to forge a friendship with President Vladimir V. Putin of Russia and has largely avoided criticizing him personally even as a special counsel, Robert S. Mueller III, investigated whether Mr. Trump’s campaign coordinated with Russia during the 2016 election. But in recent weeks, his administration has taken increasing action against Russia, and the president singled out Mr. Putin over Syria’s use of chemical weapons on Twitter and again in a televised speech on Friday night.

New sanctions on Monday would be the third round enacted by the Trump administration against Russia in the past four weeks. Last month, the administration targeted Russian companies and individuals for intervening in the 2016 election and mounting cyberattacks against Western facilities. It followed that this month with penalties against Mr. Putin’s inner circle, singling out some of Russia’s richest men and top government officials.