Speaking to reporters at the White House on Thursday, Trump said Ukraine would have a seat at the table during any peace negotiations with Russia over ending the war.
"They're part of it. We would have Ukraine, and we have Russia, and we'll have other people involved, a lot of people," Trump said.
Asked whether he trusts Putin, he said: "I believe that he would like to see something happen. I trust him on this subject."
Trump said US and Russian officials would meet in Munich on Friday and that Ukraine was also invited.
On Thursday, US Secretary of State Marco Rubio discussed "the need for bold diplomacy" to end the war in a call with Ukrainian Foreign Minister Andrii Sybiha, the State Department said.
Russia's financial markets soared and the price of Ukraine's debt rose at the prospect of the first talks in years to end Europe's deadliest war since World War Two.
Trump's unilateral overture to Putin on Wednesday, accompanied by apparent concessions on Ukraine's principal demands, raised alarm for both Kyiv and the European allies in NATO who said they feared the White House might make a deal without them.
"We, as a sovereign country, simply will not be able to accept any agreements without us," Ukrainian President Volodymyr Zelenskiy said.
He said Putin aimed to make his negotiations bilateral with the United States, and it was important that this not be allowed.
The Kremlin said plans were under way for Putin and Trump to meet, possibly in Saudi Arabia. Ukraine would "of course" participate in peace talks in some way, but there would also be a bilateral negotiation track between the United States and Russia, said Kremlin spokesman Dmitry Peskov.
The United Arab Emirates has told the United States it wants to host talks aimed at ending the war in Ukraine, Reuters reported.
European officials took an exceptionally firm line in public towards Trump's peace overture, saying any agreement would be impossible to implement unless they and the Ukrainians were included in negotiating it.
"Any quick fix is a dirty deal," European foreign policy chief Kaja Kallas said. She also denounced the apparent concessions offered in advance.
"Why are we giving them (Russia) everything that they want even before the negotiations have been started?" said Kallas.
A European diplomatic source said ministers had agreed to engage in a "frank and demanding dialogue" with US officials - some of the strongest language in the diplomatic lexicon - at the annual Munich Security Conference beginning on Friday.
On Wednesday, Trump made the first publicly acknowledged White House call with Putin since Russia's February 2022 full-scale invasion, and then followed it up with a call to Zelenskiy. Trump said he believed both men wanted peace.
But the Trump administration also said openly for the first time that it was unrealistic for Ukraine to expect to return to its 2014 borders or join the NATO alliance as part of any agreement, and that no US troops would join any security force in Ukraine that might be set up to guarantee a ceasefire.
US Defense Secretary Pete Hegseth, who unveiled the new policy in remarks at NATO headquarters, said on Thursday the world was fortunate to have Trump, the "best negotiator on the planet, bringing two sides together to find a negotiated peace".
Kremlin spokesman Peskov said Moscow was "impressed" by Trump's willingness to seek a settlement.
Russia seized Ukraine's Crimea peninsula and its proxies captured territory in the east in 2014, before its full-scale invasion in 2022 when it captured more land in the east and south.
Ukraine pushed Russian invaders back from the outskirts of Kyiv and recaptured swathes of territory in 2022, but its outmanned and outgunned forces have slowly ceded more land since a failed Ukrainian counter-offensive in 2023.
Relentless fighting has killed or injured hundreds of thousands of troops on both sides and pulverised Ukrainian cities.
Meanwhile, there has been no narrowing of positions on either side. Moscow demands Kyiv cede more land and be rendered permanently neutral in any peace deal; Kyiv says Russian troops must withdraw and it must win security guarantees comparable to NATO membership to prevent future attacks.
Ukrainian officials have acknowledged in the past that full NATO membership may be out of reach in the short term, and that a hypothetical peace deal could leave some occupied land in Russian hands.
