United States President Donald Trump said he believed Ukrainian President Volodymyr Zelensky was ready to concede Crimea to Russia as part of any ceasefire deal, as talks on a truce entered what Washington called a critical week on Monday.

Trump also stepped up pressure on Vladimir Putin, saying the Russian president should “stop shooting” and sign an agreement to end the grinding war that started with Moscow’s February 2022 invasion.

Trump’s comments came a day after he met Zelensky during the funeral of Pope Francis, breaking the ice after a major row between the US and Ukrainian leaders at the White House in February.

“Oh, I think so,” Trump told reporters in Bedminster, New Jersey, when asked whether he thought Zelensky was ready to “give up” Crimea — despite the Ukrainian president repeatedly saying he never would.

Trump added that during their talks in the Vatican they had “briefly” discussed the fate of the Black Sea peninsula, which Moscow annexed in 2014.

The 78-year-old US president, who boasted before his inauguration that he could halt Russia’s invasion of Ukraine within one day, launched a diplomatic offensive to stop the fighting after taking office in January.

Kyiv and western allies have feared that Trump was pivoting towards Moscow’s position.

But the US leader has appeared increasingly impatient with Putin in recent days.

Russia launched drone and missile attacks the night after the Vatican talks, killing four people in regions across eastern Ukraine and wounding more than a dozen.

“I want him to stop shooting, sit down, and sign a deal,” Trump said Sunday when asked what he wanted from Putin. “We have the confines of a deal, I believe, and I want him to sign it.”

The White House has said that without rapid progress, it could walk away from its role as a broker. Trump indicated that he would give the process “two weeks.”

US Secretary of State Marco Rubio earlier Sunday stressed the importance of the week ahead.

“We’re close, but we’re not close enough” to a deal to halt the fighting, Rubio told broadcaster NBC. “I think this is going to be a very critical week.”

But there is still US frustration with both sides, as the war, which has devastated swaths of eastern Ukraine and killed tens of thousands of people, drags on.

Ukraine launched a “massive” drone attack on Russia’s Bryansk region on Sunday, killing one civilian and injuring another, the regional governor said.

Washington has not revealed details of its peace plan, but has suggested freezing the front line and accepting Russian control of Crimea in exchange for an end to hostilities.

Russia claims to have annexed four eastern and southern territories of war-battered Ukraine since its full-scale invasion three years ago, despite not having full military control over them.

Russia holds about 20 percent of Ukraine’s territory, including Crimea.

But Germany’s Defense Minister Boris Pistorius said Sunday that Ukraine should not agree to all the steps reportedly set out in the deal proposed by Trump.

Kyiv knew a ceasefire “may involve territorial concessions,” Pistorius told broadcaster ARD. “But these will certainly not go... as far as they do in the latest proposal from the US president.”