US Secretary of State Marco Rubio warned Washington would "move on" from peace talks unless it saw progress soon.

But speaking on a trip to Italy, US Vice President JD Vance said he was "optimistic" about ending the three-year war.

President Donald Trump has been pressing both Moscow and Kyiv to agree a truce, but has failed to extract any major concessions from the Kremlin, despite repeated negotiations between his administration and Russia.

One of the few commitments Trump had wrangled from Russia -- a temporary moratorium on striking Ukrainian energy infrastructure -- "expired" on Friday, Kremlin spokesman Dmitry Peskov said in response to an AFP question.

Moscow has kept up strikes on Ukraine, killing at least two people and wounding dozens more in attacks on the northeastern regions of Kharkiv and Sumy, Ukrainian officials said.

After meeting European officials in Paris to discuss a ceasefire, Rubio said Washington needed to figure out soon whether a ceasefire was "doable in the short term".

"Because if it's not, then I think we're just going to move on," he told reporters.

Moments later, Vance said he did not want to prejudge the negotiations, but declared he was "optimistic" about the chances of peace.

- 'Good Friday' missiles -

Ukrainian President Volodymyr Zelensky slammed the latest attacks on his country, which came just days before Easter.

Kyiv earlier announced it had received the bodies of 909 soldiers from Russia.

"This is how Russia started Good Friday -- with ballistic missiles, cruise missiles, Shahed drones. A mockery of our people and cities," Zelensky said on Telegram.

Russia said it had hit "key drone production sites" and Ukrainian military airfields.

Since taking office, Trump has embarked on a rapprochement quest with the Kremlin that has alarmed Kyiv and driven a wedge between the United States and its European allies.

Russian President Vladimir Putin last month rejected a joint US-Ukrainian proposal for a full and unconditional pause in the conflict, while the Kremlin has made a truce in the Black Sea conditional on the West lifting certain sanctions.

Trump has also repeatedly expressed anger and frustration at Zelensky in a marked break from policy under his predecessor, Joe Biden.

The United States is pushing Ukraine into a deal that would give Washington sweeping access to its mineral resources.

Ukraine's prime minister will visit Washington next week for talks with top US officials aimed at clinching the minerals and resources deal by April 26, according to a US-Ukraine signed "memorandum of intent" published Friday.

Trump wants the deal -- designed to give the United States royalty payments on profits from Ukrainian mining of resources and rare minerals -- as compensation for aid given to Ukraine under Biden.

- Witkoff on 'Russian side' -

France hosted meetings between US and European officials in Paris on Thursday, saying the talks had launched a "positive process".

The meetings included French President Emmanuel Macron, Rubio and US envoy Steve Witkoff.

European officials had expressed dismay at being shut out from the peace process, while Ukraine has expressed concern that Witkoff -- one of Trump's closest allies -- is biased towards Russia.

Zelensky accused Witkoff on Thursday of adopting the "strategy of the Russian side," after the US envoy suggested a peace deal with Moscow hinged on the status of Ukraine's occupied territories.

"He is consciously or unconsciously, I don't know, spreading Russian narratives," Zelensky told journalists.

Witkoff told Fox News on Monday that a peace settlement depended on "so-called five territories" -- the Ukrainian regions of Donetsk, Lugansk, Zaporizhzhia, Kherson and Crimea, that Russia claims to have annexed.

The Kremlin wants its claims over the regions to be recognised as part of any peace deal, a proposal that Ukraine has balked at. Moscow does not fully control any of them except for Crimea, which it seized in 2014.

Beijing on Friday denied giving any party in the Ukraine war lethal weapons, after Zelensky claimed he had "information" China was supplying arms to Russia.

"The Chinese side has never provided lethal weapons to any party in the conflict, and strictly controls dual-use items," foreign ministry spokesman Lin Jian said.

Ukraine announced on Friday it had sanctioned three Chinese companies.