President Vladimir V. Putin of Russia on Thursday did not rule out a U.S. and Ukrainian proposal for a monthlong cease-fire, but he set down numerous conditions that would most likely delay any truce — or could make one impossible to achieve.

Mr. Putin’s comments during a news conference highlighted the balance he was trying to strike, exuding confidence in Russia’s position on the battlefield while seeking to continue talks with the United States and avoid upsetting President Trump. The U.S. president, having antagonized the country’s allies and realigned American foreign policy in Russia’s favor, has emerged as a key geopolitical partner for Mr. Putin.

Speaking at the Kremlin with the visiting president of Belarus, Aleksandr G. Lukashenko, Mr. Putin suggested that Ukraine was much more in need of a pause in the fighting than Russia was. He appeared confident that he would be able to force Ukraine to make extensive concessions, potentially including a requirement that Ukrainian soldiers in Russia’s Kursk region surrender.

“In these conditions, it seems to me that it would be very good for the Ukrainian side if there were a cease-fire, even for 30 days,” Mr. Putin said. “And we’re in favor of it. But there are nuances.”

Mr. Putin then listed those “nuances,” starting with the Ukrainian forces still in Kursk. He said that Russia would not allow those troops to withdraw peacefully and that the Ukrainian leadership could instead order them “to simply surrender.”

Ukraine stunned Russia in August with a cross-border incursion into Kursk, seizing several hundred square miles of territory. It was the first extensive fighting on Russian territory during the war, which Mr. Putin started with a full-scale invasion of Ukraine in 2022.

But Russia now appears close to pushing Ukraine out of Kursk, a development that would reduce Kyiv’s leverage in any peace talks.

Mr. Putin also suggested he might demand that Ukraine halt its mobilization of new troops and Ukraine’s Western allies stop arms deliveries, and said it was not clear how the cease-fire would be monitored along a front line of some 700 miles.

“These are all questions demanding very careful study,” Mr. Putin said.

Mr. Putin was set to meet with Steve Witkoff, Mr. Trump’s Middle East envoy, later on Thursday. The Russian leader added that he might “have a call with President Trump and talk it over with him.”

Mr. Trump, speaking with NATO’s secretary general, Mark Rutte, in the Oval Office on Thursday, said there were “very serious discussions” with Mr. Putin and others as they tried to finalize a 30-day cease-fire deal.

“We’d like to see a cease-fire from Russia,” Mr. Trump told reporters. When asked if he would speak with the Russian president, he said he would “love to meet” and talk with him.

As he has in the past, Mr. Putin said that any deal to end the fighting would need to address the “original causes” of the war — suggesting that he would push for major Western concessions, such as a reduction of NATO’s presence in Eastern Europe, though it wasn’t clear if he would make them a stipulation for a monthlong cease-fire.

But Mr. Putin also appeared to take pains to show he was ready for substantive negotiations with Mr. Trump, beginning his remarks on a cease-fire by thanking the American president for paying “so much attention to a settlement in Ukraine.”

Mr. Putin, notably, did not repeat the onerous cease-fire conditions that he laid out in a speech last summer and that Russian officials have been repeating ever since. He said at the time that Ukraine needed to withdraw in full from the four regions that Russia has claimed as its own but does not fully control.

Still, Dara Massicot, a Russian military specialist at the Carnegie Endowment for International Peace, called Mr. Putin’s new demands “very dangerous for Ukraine.” In effect, she argued, Mr. Putin was pushing for a scenario in which the West would not be able to help Ukraine rebuild its armed forces while Russian factories pumped out new weaponry.

“What Putin said today implies that the West cannot support Ukraine while Russia regenerates,” she said.

Tyler Pager and Eric Schmitt contributed reporting.