US President Donald Trump lashed out at Volodymyr Zelensky on Wednesday, blaming the Ukrainian president's refusal to accept Russian occupation of Crimea for failure to end the war.

As the leaders traded accusations, Ukrainian authorities issued an alert for an "enemy missile" attack on Kyiv, with explosions heard across the capital.

Trump said a deal was "very close" — and effectively closed with Moscow — but Zelensky was proving "harder" to negotiate with.

The Ukrainian president's refusal to accept US terms for ending the conflict — which began with Russia's invasion — "will do nothing but prolong the 'killing field'," he added.

"I think we have a deal with Russia. We have to get a deal with Zelensky," Trump told reporters. "I thought it might be easier to deal with Zelensky. So far it's been harder."

Ahead of Trump's broadside, Vice President JD Vance laid out the US vision for a peace deal where Russia would get to keep already occupied swaths of Ukraine, which include Crimea.

Zelensky has rejected this as a violation of Ukraine's constitution.

That in turn prompted an outburst from Trump, in which he accused Zelensky of being "inflammatory" and taking a position "very harmful to the Peace Negotiations with Russia."

Zelensky "can have Peace or, he can fight for another three years before losing the whole Country," Trump wrote on Truth Social.

Trump said Crimea — a lush Black Sea peninsula with longtime major Soviet and Russian naval facilities — "was lost years ago" and "is not even a point of discussion."

Zelensky responded by posting on social media a 2018 "Crimea declaration" by Trump's then-secretary of state Mike Pompeo, which said Washington "rejects Russia's attempted annexation of Crimea."

Weeks into a US-initiated process, Trump's patience was "running very thin," White House spokeswoman Karoline Leavitt said.

Intense US pressure on Ukraine to accept a deal comes after Trump regularly boasted on the campaign trail that he would resolve the conflict in 24 hours.

He has put no equivalent visible pressure on Russia, while dangling a lifting of massive US economic sanctions against Moscow if the fighting stops.

'Freeze' Russia's gains

Vance gave the fullest public explanation of the US plan so far, saying the deal would "freeze the territorial lines at some level close to where they are today."

"The Ukrainians and the Russians are both going to have to give up some of the territory they currently own," Vance said while on a trip to India.

Freezing the frontlines would mean Ukraine losing large areas to Russia.

The vice president did not explain what territory Russia, which seized Crimea in 2014 and launched a full-scale invasion targeting the rest of the country in 2022, would have to give up.

It was time for Moscow and Kyiv "to either say 'yes,' or for the United States to walk away from this process," Vance said.

Growing speculation over Washington being ready to recognize Russian rule over Crimea has alarmed European capitals.

French President Emmanuel Macron's office said "Ukraine's territorial integrity and European aspirations are very strong requirements for Europeans."

A spokesperson for UK Prime Minister Keir Starmer told reporters "it has to be up to Ukraine to decide its future."

Top Ukrainian officials wrapped up a round of talks in London on Wednesday with representatives from Britain, France, Germany and the United States.

US presidential envoy Steve Witkoff is to visit Moscow this week and Trump said he would likely meet with Russian President Vladimir Putin shortly after his trip to the Middle East in mid-May.

Russian bombing

The diplomatic wrangling and strikes on Kyiv came after a fresh wave of Russian air attacks that shattered a brief Easter truce.

A Russian drone strike on a bus in the southeastern city of Marganets killed nine people and wounded at least 30 more, the Dnipropetrovsk regional governor said Wednesday.

Ukrainian authorities also reported strikes in the regions of Kyiv, Kharkiv, Poltava and Odesa.

In light of the attacks, Zelensky called for an "immediate, full and unconditional ceasefire."