The US has announced a meeting on Tuesday on the military situation in Ukraine, with Secretary of Defense Lloyd Austin hosting it at Germany's Ramstein Air Force Base.
Ministry spokesman John Kirby did not say how many allies should participate.
According to Ukrainian President Volodymyr Zelenskyy, Russia has meanwhile rejected the proposal for a ceasefire over the Orthodox Easter holidays.
Moscow is also moving more troops for the war in Ukraine.
Recently, Russian units have apparently been able to make isolated advances in the Donbass.
The federal government wants to provide funds for reconstruction in Ukraine.
Fridays for Future wants to demonstrate across Europe against gas from Russia this Friday.
Zelensky said that the cancellation of a ceasefire for the Easter celebrations of Orthodox Christians this weekend shows what the Christian faith and one of the happiest and most important holidays mean to the leaders of Russia.
"But we'll still have hope.
The hope for peace, the hope that life will triumph over death," said Zelenskyy.
Among other things, Pope Francis had called for a ceasefire in the run-up to the Easter festival of orthodox Christians this weekend.
Orthodox Christians celebrate Easter on April 24 this year.
They are the largest religious group in Ukraine.
Zelenskyj: Continued resistance in Mariupol
According to Zelenskyy, resistance in the port city of Mariupol continues.
The city continues to resist Russia, he said on Friday night.
"Despite what the squatters say about them."
Russian President Vladimir Putin declared the city conquered on Thursday.
However, according to Russian information, more than 2,000 Ukrainian fighters and foreign mercenaries are holed up in the Azovstal steelworks there.
So far they have not responded to Putin's demands to lay down arms.
Putin did not order a storm, but a hermetic sealing off of the site.
According to the US war research institute ISW, it is "rather unlikely" that a reduction in the pace of operations in Mariupol will now free up significant forces for Russian offensives elsewhere in the east.
According to the latest ISW analysis, Russian tactical battalions have suffered heavy losses in the battle for the city and need time to be deployed.
Some of the troops deployed there are also needed for several other missions, including the siege of the Asovstal plant and securing the rest of the city.
Ukraine: Russian forces take 42 locations in Donetsk
According to an adviser to the Ukrainian presidential office, Russian troops occupied 42 towns in the Donetsk region in the east within 24 hours.
All in all, Russian units are currently controlling more than 3,500 locations across Ukraine, said Olena Simonenko on Friday night on Ukrainian unity television.
Recently, Russian advances in the Luhansk region had also been reported.