Ukrainian President Volodymyr Zelensky visited Washington Thursday to appeal for help fighting Russia, winning warm words of support and weapons from Joe Biden but confronting skeptical Republicans who want to cut off aid, AFP reported.

"We're with you and we're staying with you," Biden told the Ukrainian leader after their top teams met at the White House to thrash out Zelensky's demands for more arms to push back the Russian military operation.

Wearing his trademark olive green military-style shirt, Zelensky said Ukraine "has exactly what our soldiers need" after Biden announced a new package of US military aid, including sophisticated air defense weapons.

But behind the visuals -- firm handshakes across a grand cabinet table and shows of solidarity in the Oval Office -- lay the fact that Zelensky's second wartime trip to Washington was far tougher than the first.

Where Zelensky received a hero's welcome when he visited in December, this time he spent his closed-door meetings in the US Congress desperately trying to overcome growing war fatigue from Republicans.

Hardline Republicans are threatening to block Democrat Biden's request for a fresh $24 billion aid package for Ukraine, and it has now become caught up in a bitter spending battle that could spark a US government shutdown.