U.S. President Donald Trump on Monday set a 10- to 12-day deadline for Russia to show progress toward ending its war in Ukraine, escalating pressure on Moscow.
Trump, who is holding meetings in Scotland, said earlier Monday that he was going to shorten a 50-day deadline he had set because of frustration with Russian President Vladimir Putin.
The U.S. president said he was "very disappointed" with Russian President Vladimir Putin, criticizing his decision to continue airstrikes against civilian targets in Ukraine.
Speaking alongside Starmer outside his hotel in Turnberry, South Ayrshire, Trump said: "We thought we had it settled numerous times, and then President Putin goes out and starts launching rockets into some city like Kiev and kills a lot of people in a nursing home or whatever.
"You have bodies lying all over the street, and I say that's not the way to do it. So we'll see what happens with that."
Earlier this month, Trump threatened to impose "very severe" tariffs on Russia if Putin did not agree a ceasefire within 50 days, with the deadline due to expire on September 2.
But on Monday, he said he would "reduce that 50 days that I gave him to a lesser number", adding: "I think I already know the answer, what's going to happen."
Efforts to secure a ceasefire in Ukraine are expected to feature on the agenda for Starmer's meeting with Trump on Monday, along with the situation in Gaza and progress on implementing the UK-US trade deal.
Last week, London said both men were "set to talk about their shared desire to bring an end to the barbaric war" and "reflect on progress in their 50-day drive to arm Ukraine and force Putin to the negotiating table".
Meanwhile, the conflict in Ukraine continues, with Russian drone and missile strikes hitting the country's north-eastern Sumy region on Sunday, wounding four people.
Russian officials also claimed to have shot down 150 Ukrainian drones, with one person killed and three others injured near St Petersburg.
