US President Joe Biden on Wednesday signed legislation authorizing desperately needed military aid for Ukraine, saying Washington would begin sending new assistance to Kyiv within hours.

The passage of the $95 billion package -- which also includes aid for Israel and Taiwan and a measure to potentially ban TikTok in the United States -- comes after months of delay that saw Ukrainian forces run short of ammunition and suffer battlefield setbacks.

"I just signed into law the national security package that was passed by the House of Representatives this weekend, and by the Senate yesterday," Biden told reports, saying he is "making sure the shipments start right away, in the next few hours."

"It's going to make America safer, it's going to make the world safter and it continues American leadership in the world and everyone knows it," Biden said of the legislation.

"It gives vital support to America's partners so they can defend themselves against threats to their sovereignty and to the lives and freedoms of their citizens."

The aid legislation only passed the House of Representatives after months of acrimonious debate among lawmakers over how or even whether to help Ukraine -- which Russia invaded in February 2022 -- defend itself.

A similar aid package passed the Senate in February, but had been stalled in the House while Republican Speaker Mike Johnson -- heeding calls from ex-president Donald Trump and his hardline allies -- demanded concessions from Biden on immigration policies, before a sudden reversal.

The United States has been a key military backer of Ukraine, but Congress had not approved large-scale funding for Kyiv for nearly a year and a half, and the financing of the war has become a point of contention ahead of a presidential election in November.

Ukraine's military is facing a severe shortage of weapons and recruits as Moscow exerts constant pressure from the east, with frontline circumstances are expected to worsen in the coming weeks.