Washington: US President Donald Trump said Thursday that Washington and NATO allies were "stepping up the pressure" to end the war in Ukraine, after his outreach to Russia's Vladimir Putin failed to achieve a ceasefire.

"Yeah, we are stepping up the pressure," Trump said in the Oval Office during a meeting with Finnish President Alexander Stubb when asked by an AFP reporter if he would increase efforts for a deal.

"We're stepping it up together. We're all stepping it up. NATO has been great," he added.

Trump this week brokered a peace deal in Gaza between Israel and Hamas, but has said that the war sparked by Russia's 2022 invasion of Ukraine was proving even harder to solve.

Trump hosted Putin in Alaska in August but failed to achieve a breakthrough, and since then Russia's attacks on Ukraine have escalated.

Russia said Wednesday that momentum towards reaching a peace deal in Ukraine had largely vanished following the meeting.

Stubb said he was confident that Trump would be able to push through a deal on Ukraine following the Gaza deal between Israel and Hamas.

"I think this one will be the next big one," Stubb told reporters. (AFP)