The announcement follows a virtual summit between Putin and US President Joe Biden during which Biden told Putin there would be a strong US response if Russian forces massed on Ukraine's border went on the attack.

The United States and European allies have worked to bolster Ukraine's military since 2014 when the country's armed forces crumbled in the face of Russian pressure.

Biden talked with the leaders of Britain, France, Germany and Italy on Monday to coordinate his message ahead of the summit, and the White House said he would speak again to the four countries after he was finished with Putin.