President Donald Trump held a high-stakes phone call with Russian President Vladimir Putin on Monday as he continued his push for an end to Moscow’s 3-year-old invasion of Ukraine after last week’s peace talks in Istanbul, Turkey.

Trump, in a post to his conservative social media platform, said the call lasted two hours and that he believed it went “very well.”

“Russia and Ukraine will immediately start negotiations toward a Ceasefire and, more importantly, an END to the War,” the president wrote. “The conditions for that will be negotiated between the two parties, as it can only be, because they know details of a negotiation that nobody else would be aware of.”

Trump said the talks would begin “immediately” and that he spoke with Ukrainian President Volodymyr Zelenskyy, as well as several NATO leaders, after the call with Putin.

“The Vatican, as represented by the Pope, has stated that it would be very interested in hosting the negotiations. Let the process begin!” Trump wrote.

Putin, speaking to journalists in Sochi, claimed that he is willing to work on a “memorandum on a possible future peace agreement” with Ukraine, but did not elaborate on what that would look like.

“The question is, of course, that the Russian and Ukrainian sides show their maximum desire for peace and find the compromises that would suit all parties,” Putin added.

ABC News Senior Political Correspondent Rachel Scott pressed White House press secretary Karoline Leavitt earlier Monday if Trump would set a new deadline for peace talks during his conversation with Putin. Leavitt said she wouldn’t get ahead of Trump on any specific timeline.

“His goal is to see a ceasefire and to see this conflict come to an end, and he’s grown weary and frustrated with both sides of the conflict,” she said of the president.

Leavitt also said she believed Trump “would certainly be open” to meeting with Putin but “let’s see how this call goes today.”

Renewed direct contact with Putin — the last publicly known direct phone call between the two presidents took place in February — comes after Trump’s hopes for peace talks progress in Istanbul were scuppered, Putin having declined to attend despite Zelenskyy’s invitation to do so.

The Istanbul talks were the first known meeting between representatives of Moscow and Kyiv since spring 2022, when the Turkish city hosted the final round of unsuccessful peace negotiations to end Russia’s unfolding invasion.

Once it became clear Putin would not attend, Trump told reporters of the peace effort, “Nothing’s going to happen until Putin and I get together, okay?”

“And obviously he wasn’t going to go,” Trump added. “He was going to go, but he thought I was going to go. He wasn’t going if I wasn’t there. And I don’t believe anything’s going to happen, whether you like it or not, until he and I get together, but we’re going to have to get it solved, because too many people are dying.”

On Monday, Vice President JD Vance said the U.S. is “more than open to walking away” from negotiations.

“We realize there’s a bit of an impasse here,” Vance told reporters, “and I think the president’s going to say to President Putin, ‘Look, are you serious? Are you real about this? Because the proposal from the United States has always been, look, there are a lot of economic benefits to thawing relations between Russia and the rest of the world, but you’re not going to get those benefits you keep on killing a lot of it is lot of innocent people.’”

Trump’s repeated threats of further sanctions on Russia have so far failed to precipitate any notable shift in Moscow’s war goals — which, according to public statements by officials, still include Ukraine’s ceding of four regions — which Russian forces do not fully control — plus Crimea, as well as a permanent block on Kyiv’s accession to NATO.

Putin said Sunday that any peace deal with Ukraine should “eliminate the causes that triggered this crisis” and “guarantee Russia’s security.”

Kyiv and its European backers are still pushing for a full 30-day ceasefire, during which time they say peace negotiations can take place. Moscow has thus far refused to support the proposal, suggesting that all Western military aid to Ukraine would have to stop as part of any ceasefire.

Contacts between U.S., Russian and Ukrainian officials continued after the end of the talks in Istanbul. On Saturday, Secretary of State Marco Rubio spoke with Russian Foreign Minister Sergey Lavrov.

State Department spokesperson Tammy Bruce said Rubio welcomed a prisoner exchange agreement reached during the Istanbul meeting and emphasized Trump’s call for an immediate ceasefire.

Ukrainian Foreign Minister Andrii Sybiha on Monday wrote on X that the Istanbul meeting highlighted a “stark difference” between Moscow and Kyiv. “Ukraine is forward-looking, focused on the full and immediate ceasefire to kickstart the real peace process.”

“To the contrary, Russia is completely focused on the past, rejecting the ceasefire and instead talking constantly about the 2022 Istanbul meetings, attempting to make the same absurd demands as three years ago,” the foreign minister said.

“This is yet another reason why pressure on Russia must be increased,” Sybiha added. “Moscow must now understand the consequences of impeding the peace process.”

Meanwhile, long-range strikes by both sides continued. On Sunday night into Monday morning, Ukraine’s air force said Russia launched 112 drones into the country, 76 of which were shot down or jammed. Damage was reported in five regions of Ukraine, the air force said in a post to Telegram.

Russia’s Defense Ministry said on Monday morning that its forces had downed 35 Ukrainian drones overnight.

ABC News’ Hannah Demissie, William Gretsky and Tanya Stukalova contributed to this report.