US President Joe Biden on Sunday reaffirmed Washington’s commitment to “Ukraine’s sovereignty and territorial integrity” to Ukrainian President Volodymyr Zelensky. The United States has said there is a “clear possibility” of a Russian attack on Ukraine in the coming days.

Biden spoke by telephone with the Ukrainian president. Western officials have expressed fears that Russian President Vladimir Putin could invade in the next few days. Information has already been received that there is a danger of an attack on Ukraine by Wednesday.

The White House said in a statement that Biden “made it clear to Zelensky that the United States, along with its allies and allies, would respond swiftly and decisively to any further Russian aggression against Ukraine.” Biden, however, ruled out sending troops to fight in Ukraine if Russia invaded.

However, he promised to impose “quick and tough” economic sanctions. The White House said Biden and Zelensky “agreed on the importance of continuing diplomacy and resistance” to the Russian attack. But Western diplomatic proposals to Putin have so far failed to break the deadlock.

Meanwhile, several international airlines have suspended flights to Ukraine due to the threat of war. However, Ukraine has stated that it has not declared its airspace closed. KLM Airlines of the Netherlands said on Saturday that it had canceled its flight to Ukraine until further notice.