US President Joe Biden has had a phone conversation with Ukrainian counterpart Volodymyr Zelensky on Sunday when he stated that Washington  will "respond decisively" if Russia decides to invade Ukraine. 

The White House press secretary Jen Psaki also stated that Biden expressed support for diplomatic efforts including planned talks between top American and Russian officials set for January 9 and 10 in Geneva.

Biden also reaffirmed the United States'  ‘strong commitment’ to Ukraine’s sovereignty and territorial integrity. 

Russia is building up its troops at Ukrainian borders, making threats for a repeated aggression. 

It has recently demanded NATO to break its promise given to Georgia and Ukraine at the 2008 Bucharest Summit on the membership of the countries.