Donald Trump has held out the prospect of US security guarantees and a trilateral meeting with Vladimir Putin and Volodymyr Zelenskyy to end the war in Ukraine.

At the start of a series of crunch meetings in Washington on Monday, both Trump and Zelenskyy struck more emollient tones than at a previous encounter in February, when the Ukrainian leader was ejected from the White House.

“There’ll be a lot of help when it comes to security,” the US president said, referring to plans to bolster Ukraine’s defences in the event that the conflict with Russia is resolved.

In a reference to European countries, represented at the White House by seven leaders on Monday, he added: “They are first line of defence because they’re there, they’re Europe, but we’re going to help them out also. We’ll be involved.”

On Monday, Trump also suggested he hoped to arrange a three-way meeting with the Russian and Ukrainian presidents. Zelenskyy has long sought a top-level meeting with Putin, though the Kremlin has shown little indication of agreeing unless Ukraine accepts its maximalist demands.

“If everything works out today, we will have a trilat and I think there will be a reasonable chance of ending the war if we do that,” he said.

“The war is going to end when it ends. I can’t tell you [when], but the war is going to end, and this gentleman [Zelenskyy] wants it to end, and Vladimir Putin wants it to end,” Trump said in the Oval Office.

The US president said he would call Putin following the White House summit. “We’re going to have a phone call right after these meetings today, and we may or may not have a trilat,” Trump said.

He said he had spoken to Putin “indirectly” before sitting down with Zelenskyy. 

Asked if peace could involve US troops on the ground in Ukraine, Trump said that he would potentially answer that question later in the day.

“Seven great leaders of great countries also, and we’ll be talking about that, they’ll all be involved . . . there’ll be a lot of help when it comes to security.”

Leaders including Sir Keir Starmer of the UK, France’s Emmanuel Macron, Nato secretary-general Mark Rutte and European Commission president Ursula von der Leyen were due to meet Trump later in the day.

The Ukrainian leader and his allies have been urging Trump to spell out the security guarantees the US would offer Kyiv to help it reach a truce with Moscow.

Asked what he needs from the US and Europeans in regards to security guarantees, Zelenskyy said: “Everything.”

“First, a strong Ukrainian army. And it’s a lot about weapons, training issues and intelligence,” Zelenskyy said.

He said more specifics would be discussed between him, Trump and the European leaders on Monday.

The meetings come amid concerns in Kyiv and major European capitals that Trump has swung behind Putin’s proposals to end the war following their Friday meeting in Alaska, and will demand that Ukraine makes major concessions on land.

Zelenskyy has said that ceding any land that Russia does not control and officially recognising that which his forces occupy is a firm red line.

But Trump appeared to pile further pressure on to Ukraine late on Sunday, when he said Zelenskyy could end the war “almost immediately, if he wants to”.

Russia’s foreign ministry reiterated its opposition to any Nato troop deployments in Ukraine on Monday. Moscow has also previously demanded caps on Ukraine’s military, as well as an end to western arms supplies and intelligence sharing.