Ukrainian peace negotiators in Miami have been used as a "smokescreen" for a "weak" decision by Donald Trump to lift diesel sanctions on Russia Volodymyr Zelenskyy said in a furious response to the US president's backflip on Russian sanctions.

In a move likely to create a fresh crisis with Washington's Nato allies, Trump announced the deal with Putin on his Truth Social network, saying it was essential to reduce fuel prices in the US, which have soared as a result of his decision to go to war with Iran.

The Ukrainian president, who flew to Washington last month to plead with US lawmakers to pass tougher sanctions on Russia, said in a statement on Friday that it was "unfortunately, a weak decision by strong partners".

"I believe our team is simply being used as a smokescreen. And that is certainly not fair. It is certainly not how partners should treat each other."

Negotiators for the US, Ukraine and Europe held six hours of talks in Miami on Friday with the aim of reaching agreement on ending the war in Ukraine a source briefed on the talks said.

They discussed a postwar economic package for Ukraine and potential new security architecture between Europe and Russia, the source said.

President Trump announced the diesel deal as his envoy Steve Witkoff and son-in-law Jared Kushner were meeting with Ukrainian officials in Florida to discuss a peace plan.

Trump's announcement was a betrayal of Ukraine, the European allies and US national security, said Senate Democratic leader Chuck Schumer top Democrat on the Foreign Relations Committee Sen. Jeanne Shaheen, and senior Democrat senator, Elizabeth Warren. "Enough is enough," the senators wrote. "The President must end his war with Iran instead of funding Russia's war machine."

A number of prominent Republicans joined Democrats on Friday to condemn Trump for lifting the diesel sanctions including congressman Don Bacon, who said the majority of Americans supported Ukraine. "The President's policies towards Russia and Ukraine are failures. We need moral clarity not moral ambiguity."

Ukraine struck and partly disabled a major datacentre operated by Russian technology company Yandex on Friday in the second such action in successive days. Yandex, which is heavily involved in Russia's AI development, said its data centre in the Kaluga region south-west of Moscow had been struck by Ukrainian drones and partly put out of action. Ukrainian arms maker Firepoint said Kyiv had used its FP-1 one-way attack drones to mount the strike.

Four Ukrainians were arrested in Vienna this week on suspicion of spying Austrian interior minister, Gerhard Karner, said on Friday, with Ukrainska Pravda newspaper saying two of its team were among those detained. Three remain in custody, Karner said, declining to provide further details because the investigation was ongoing. Austrian news agency APA quoted a spokeswoman for the Ukrainian embassy in Vienna as saying it was awaiting an explanation from the Austrian authorities on the circumstances of and legal grounds for the arrests. The embassy did not immediately respond to a request for comment.

Russian forces struck three cargo vessels in and around Ukraine's Black Sea ports on Friday Russia's defence ministry said. The ministry said one vessel was hit in the port of Mykolaiv, another in the port of Chornomorsk and a third, bound for Odesa, in the Black Sea. According to the ministry, all three vessels were being used to supply the Ukrainian military. Reuters could not independently verify the report or the claim.

Russian strikes killed three people and wounded at least eight across Ukraine, officials said Friday as Ukraine struggles to counter escalating Russian bombardments that have killed more than 50 people over the past three days.