President Volodymyr Zelensky urged US House of Representatives Speaker Mike Johnson to quickly pass a new $60 billion military and financial aid package for Ukraine.
The bill has been held up in Congress for months.
Zelensky emphasized the importance of unifying support for Ukraine in the face of differing views.
Ukrainian troops are facing artillery supply shortages as US aid is delayed in Congress and EU promised munitions are not delivered on time.
Ukrainian President Volodymyr Zelensky met with British Prime Minister
Boris Johnson to discuss the current situation on the battlefield and Russia's increased use of air strikes against Ukraine's energy system.
Last week, Russia carried out its largest air strike since invading Ukraine in February 2022, damaging power units at a major dam and causing blackouts for over a million people.
Moscow has described these attacks as "revenge" strikes in response to Ukrainian attacks on Russian regions.
Russia has been using harder-to-stop ballistic missiles and denies targeting civilians, but many have been killed in its strikes.