US President Joe Biden has announced more than $US8 billion ($A12 billion) in military assistance for Ukraine to help Kyiv "win this war" against Russian invaders, using a visit by President Volodymyr Zelenskiy to make a major commitment.
The aid includes the first shipment of a precision-guided glide bomb called the Joint Standoff Weapon, with a range of up to 130km.
The medium-range missile gives Ukraine a major upgrade to the weapons it is using to strike Russian forces, allowing the Ukrainians to do it at safer distances.
The bomb, capable of striking targets with high accuracy, is to be dropped from fighter jets. Biden will not announce that Washington would let Ukraine use US missiles to hit targets deeper in Russia, a US official said.
Supporting Ukraine, which Russia invaded in February 2022, has been a US top priority, Biden said in a statement.
"That is why, today, I am announcing a surge in security assistance for Ukraine and a series of additional actions to help Ukraine win this war," said Biden, who leaves office in January.
The bulk of the new aid, $US5.5 billion, is to be allocated before Monday's end of the US fiscal year, when the funding authority is set to expire.
Another $US2.4 billion is under the Ukraine Security Assistance Initiative, which allows the administration to buy weapons for Ukraine from companies rather than pull them from US stocks.
This will provide Ukraine with additional air defence, unmanned aerial systems and air-to-ground munitions, as well as strengthen Ukraine’s defence industrial base and support its maintenance and sustainment requirements, Biden said.
Under his plan, the president said, the Defense Department will refurbish and provide Ukraine with an additional Patriot air defence battery and more Patriot missiles.
Biden ordered the Pentagon to expand training for Ukrainian F-16 pilots, including by supporting the training of an additional 18 pilots in 2025.
To combat Russian sanctions evasion and money laundering, the US will act to disrupt what Biden called "a global cryptocurrency network, in coordination with international partners".
Biden said he will convene a leader-level meeting of the Ukraine Defense Contact Group in Germany in October to co-ordinate efforts of more than 50 countries supporting Ukraine.
Before meeting Biden at midday, Zelenskiy is due to meet Democratic and Republican leaders at the Capitol.
Ukraine's defence has largely received bipartisan support in the US, but it was not clear how many Republicans would make time to sit down with Zelenskiy amid rising criticism of his government from party leaders, including Donald Trump, the Republican presidential candidate.
Trump has been criticising the Ukrainian president as he campaigns for the November 5 election and, at least for now, turned down a request from Zelenskiy for a meeting.
The former president was sharply critical of Zelenskiy on Wednesday, telling a campaign rally in North Carolina, "We continue to give billions of dollars to a man who refused to make a deal, Zelenskiy."
Trump also blamed Biden and Vice President Kamala Harris, his Democratic presidential opponent, for allowing Russia's invasion.
Many congressional Republicans have been furious about Zelenskiy's visit on Sunday to a munitions factory in Scranton, Pennsylvania, where Biden grew up. The Republican-led House of Representatives Oversight Committee opened an investigation into Zelenskiy's trip.
House Speaker Mike Johnson, a Republican who is not expected to meet Zelenskiy on Thursday, demanded that he fire his ambassador to Washington for planning the Scranton trip, although he told reporters this demand was not a threat to oppose military aid.
with Reuters
