MOSCOW, November 23. /TASS/. The Kremlin regrets the United States’ walkout from the Treaty on Open Skies, because without the American side participating in it the document loses viability, Russian presidential spokesman Dmitry Peskov told the media on Monday.

"With the United States’ pullout the treaty will lose viability, of course," Peskov said. "We regret this. We believe that the treaty is an important means of building up mutual trust and keeping weapons under control," Peskov said about the US decision.

He recalled that the Russian side "from the very outset, when the US declared the intention of quitting that agreement, warned that this step would have negative consequences."

Washington on Sunday officially confirmed that the United States was no longer a participant in the Treaty on Open Skies. The statement concerning the withdrawal from the treaty was issued by the Department of State.

The incumbent US president, Donald Trump, on May 21 declared the United States’ intention to leave the Treaty on Open Skies, which allows its signatories to make flights over any territories of each other to monitor military activity. The American side alleged that Russia had violated the agreement. Moscow dismissed these charges, saying that it remained committed to the treaty all along, and put forward its own counterclaims.

The Democratic Party’s Joseph Biden, who according to US media forecasts, emerged the winner in the US presidential election, described Trump’s decision regarding the Open Skies Treaty as a shortsighted step. He warned that it would breed West-Russia tensions and increase conflict risks.