US President Donald Trump and Ukrainian leader Volodymyr Zelenskiy have discussed efforts to revive peace talks with Russia and a deal to allow Ukraine to make Patriot missile interceptors.
Zelenskiy held a private meeting with Trump in the Oval Office, in the absence of reporters, before the funeral of US senator Lindsey Graham in the afternoon.
The visit offered Zelenskiy an opportunity to shore up military support at a moment when US-Ukraine relations are warmer than they have been in months.
Zelenskiy said on Telegram that he had a "good meeting" with Trump and they had discussed the US leader's promise at a NATO summit this month to grant Ukraine a licence to produce Patriot missile interceptors.
As Russia has stepped up its attacks on cities, Ukraine has run chronically low on supplies of Patriots, which remain the only weapon in its arsenal capable of downing ballistic missiles.
"We talked with the president about licences for producing interceptors for the Patriots and other ideas that could help," Zelenskiy said, without providing further details.
"We also talked about diplomacy - it is important to step up the diplomatic process," he said, referring to stalled peace talks with Russia to end the war, now in its fifth year.
Following Graham's funeral, Zelenskiy is expected to go to the US Capitol for a meeting with senators.
The Senate is preparing to vote on a bipartisan package of new sanctions on Russia that Graham spent his final days trying to push across the finish line.
Zelenskiy's visit came after a letter sent to lawmakers from the Pentagon showed Trump's administration has told Congress it will not finish spending $US400 million ($A574 million) authorised for aid to Ukraine until fiscal year 2029.
Democrats and some of Trump's fellow Republicans have criticised the Pentagon for sitting on aid for Ukraine that members of both parties backed last year.
Zelenskiy and Trump clashed repeatedly in the early months of Trump's second term but relations between the two have improved in recent months as Ukraine has had greater success in the war, including with increased attacks on Russia's oil industry.
Ahead of the Oval Office meeting, a White House official said Trump would discuss the peace process between Russia and Ukraine with the Ukrainian president.
"Now is the time to end the war," the US official said.
Zelenskiy spoke last week with US envoys Steve Witkoff and Jared Kushner about the prospects for renewed peace talks with Russia and said Ukrainian and US officials could meet in the United States in the coming days.
