Ukrainians on Tuesday welcomed President Trump’s announcement that he would send additional weapons to fend off Russian attacks, even if it was the latest in a series of flip-flops on his approach to the war.

Lawmakers and analysts in Kyiv, Ukraine’s capital, said they were not expecting a full turnaround on military assistance, given Mr. Trump’s skepticism of U.S. spending on Ukraine and his fickleness on continuing military aid already funded by Congress.

When Mr. Trump’s administration last week decided to pause some already-approved arms transfers to Ukraine, officials said that the reason was to review weapons levels in American stockpiles.

But on Monday, Mr. Trump said that Moscow’s recent attacks on Ukrainian cities had left him no choice but to send more weapons. “We have to,” Mr. Trump said. “They have to be able to defend themselves.” He added that he had become unhappy with President Vladimir V. Putin of Russia, who has been foot-dragging in cease-fire talks that began in February.

On Tuesday, during a televised cabinet meeting in Washington, Mr. Trump again suggested Mr. Putin was not bargaining in good faith. “We get a lot of bullshit thrown at us by Putin, if you want to know the truth,” Mr. Trump said. “He’s very nice to us all the time, but it turns out to be meaningless.”

Iryna Gerashchenko, a member of the Ukrainian Parliament for the opposition European Solidarity Party, wrote on social media that the announcement on Monday was “a signal of political change.”

“The increasing intensity of Russian attacks and growing pressure from allies in Europe, particularly Germany and France, are forcing the White House to change,” she added.

A former Ukrainian prime minister, Arseniy Yatsenyuk, posted, “Thank you, Mr. President!”

Others aired skepticism that arms supplies would continue, given Mr. Trump’s earlier zigzags on weapons shipments and his wobbly backing for sanctions on Russia.

Under the Trump administration, Ukraine can no longer count on U.S.-donated weapons as American policy focuses on the Middle East and Pacific region, said Maksym Skrypchenko, president of the Transatlantic Dialogue Center, a research group in Kyiv.

“It’s not the ideal strategy we would like to see,” Mr. Skrypchenko said. “But we need to adapt to it, and we should find a place for Ukraine in that strategy.”

Mr. Trump’s about-face came after a grim week for Ukrainians that included Russia’s launching its largest aerial bombardment of the war as well as the pause in weapons shipments.

The pause was the second this year by the Trump administration, after a brief suspension of military and intelligence cooperation in March. That came after Mr. Trump publicly upbraided Ukraine’s president, Volodymyr Zelensky, in an Oval Office meeting.

The Trump administration has given other conflicting signals about how fully it supports Ukraine.

The administration has voted with Russia at the United Nations, imposed tariffs on Ukraine but not Russia, resisted enacting new sanctions on Russia and revived diplomatic relations with Moscow even as cease-fire talks stalled. At the same time, Mr. Trump has voiced disapproval of Mr. Putin and this year called him “crazy” for bombing Kyiv.

The latest turnaround raises hopes that Ukrainian air defenses will obtain sufficient Patriot interceptors to counter ballistic missile attacks and that frontline soldiers will receive ammunition to hold the line. Longer term, Mr. Zelensky has not asked for a resumption of arms donations but for approval to purchase U.S. weapons directly from American companies with financing from Europe.

In another positive signal for Ukraine, Senator Lindsey Graham said in a social media post on Monday that he expected a sanctions bill to progress in the Senate. The bill could impose what Mr. Graham has called “bone crushing” secondary sanctions on countries trading with Russia to use as leverage in cease-fire talks. “It’s time to end this bloodbath,” Mr. Graham wrote.

After Mr. Zelensky met with U.S. businesses operating in Ukraine, including Boeing and Baker Hughes, to seek support in lobbying the Trump administration, the American Chamber of Commerce in Kyiv issued a statement on July 4 appealing for more American military aid.

The statement asked Mr. Trump to “protect American businesses in Ukraine by urgently providing the defense equipment needed to stop these attacks.” More than half of the about 600 members of the chamber, the statement said, have suffered damage to offices, factories or other assets from the Russian invasion.

Members of Parliament in Kyiv have for weeks been saying that the Trump administration’s cease-fire talks have failed and that more pressure must be brought to bear on Moscow.

Halyna Yanchenko, an independent lawmaker who caucuses with Mr. Zelensky’s political party, said in an interview that Ukraine had succeeded in demonstrating to the Trump administration that Moscow, not Kyiv, was to blame for stalled talks.

Russia’s strategy has been to deplete Ukraine’s air defense ammunition while trying to win ground in the east, Oleksandr Merezhko, chairman of the foreign affairs committee in the Ukrainian Parliament, said in an interview. Kyiv has so far maintained Mr. Trump’s engagement despite his administration’s focus on the Middle East and China, and even with little apparent hope of a swift solution in Ukraine.

“He now realizes he cannot expect Putin to negotiate seriously,” Mr. Merezhko said of Mr. Trump. “There will be no quick cease-fire.”