Trump has threatened both sanctions on Russia and buyers of its exports unless progress is made.
Speaking in Scotland, where he is holding meetings with European leaders and playing golf, Trump said he was disappointed in Putin and shortening a 50-day deadline he had set on the issue earlier this month.
"I'm going to make a new deadline of about ... 10 or 12 days from today," Trump told reporters during a meeting with UK Prime Minister Keir Starmer.
"There's no reason in waiting ... We just don't see any progress being made."
The US president has repeatedly voiced exasperation with Putin for continuing attacks on Ukraine despite US efforts to end the war.
Before returning to the White House in January, Trump, who views himself as a peacemaker, had promised to end the three-and-a-half-year-old conflict within 24 hours.
"I'm disappointed in President Putin," Trump said on Monday.
"I'm going to reduce that 50 days that I gave him to a lesser number because I think I already know the answer what's going to happen."
There was no immediate comment from the Kremlin.
Ukrainian President Volodymyr Zelenskiy praised Trump for his "expressed determination" in calling for a shortened deadline.
"Clear stance and expressed determination by @POTUS - right on time, when a lot can change through strength for real peace," Zelenskiy wrote on the X social media platform.
"I thank President Trump for his focus on saving lives and stopping this horrible war."
In his nightly video address, Zelenskiy again praised Trump's "particularly significant" statement in the light Russia's "constant attempts to inflict pain on Ukraine" through air strikes on its cities.
Ukraine, he said, viewed the imposition of tough sanctions on Russia as a "key element" in ending the war.
"Russia pays attention to sanctions, pays attention to such losses," he said.
"Ukraine is ready to work productively with the United States, to work with President Trump to end this war with dignity and a secure, lasting peace."
