The United States will act swiftly to provide new military assistance to help Kyiv in its battle against Russia's invasion, President Joe Biden told his Ukrainian counterpart Volodymyr Zelensky in a Monday call.

The US House of Representatives last week greenlighted a huge and long-delayed foreign aid package that included $61 billion for war-torn Ukraine, and the Senate is expected to follow suit.

According to a White House readout, Biden underscored America's "lasting commitment" to Ukraine "as it defends its freedom against Russian aggression."

Biden told Zelensky the United States will "quickly provide significant new security assistance packages to meet Ukraine's urgent battlefield and air defense needs" as soon as the Senate passes the aid package and Biden signs it into law."

The Senate is expected to take up the measure, which has bipartisan support, on Tuesday.

"President Biden also underscored that the US economic assistance will help maintain financial stability, build back critical infrastructure following Russian attacks, and support reform as Ukraine moves forward on the path of Euro-Atlantic integration," the readout said.

Zelensky posted on social media that he thanked Biden during the call for his "unwavering support" for Kyiv.

Biden "assured me that he will sign the bill immediately as soon as it is approved by the Senate," Ukraine's president said. 

Zelensky said Biden told him the weaponry and other hardware provided in the upcoming military aid package "will be powerful, strengthening our air defense as well as long-range and artillery capabilities."

Zelensky also said the leaders discussed the latest strikes in "Russia's air terror," including bombardments by Moscow's forces which toppled a major television tower in the Ukrainian city of Kharkiv minutes before the two men spoke.