Biden "will convene a call with the leaders of the Bucharest Nine group of our eastern flank NATO Allies to brief them on his call with President Putin, hear their perspectives on the current security situation, and underscore the United States' commitment to transatlantic security," a statement said Wednesday.

The Bucharest group comprises Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania and Slovakia.

The White House said Biden would be holding the conference call after he speaks to Ukraine's President Volodymyr Zelensky, who has appealed for more US help in warding off threats of further Russian attacks.

Western countries say they are deeply concerned by the buildup of around 100,000 Russian troops on the Ukrainian border.

Russia has already has seized the Crimean peninsula and backed a separatist rebellion since 2014.

Moscow says the additional troops are there to defend against Ukraine being absorbed into the US-led NATO military alliance, although Ukraine is nowhere close to being accepted in the group.

Biden and Putin discussed the tension during a two-hour video summit on Tuesday.