MOSCOW, Nov. 23 (Xinhua) -- The U.S. pullout from the Treaty on Open Skies, a major international arms control agreement, is regretful, Kremlin spokesman Dmitry Peskov said Monday.

The U.S. exit poses a threat to the agreement's viability, Peskov told a daily briefing, who praised the pact as "a vital link" that helps strengthen mutual trust in arms control.

Moscow will seek firm guarantees that the states remaining in the treaty fulfill their obligations, the Russian Foreign Ministry said in a statement Sunday.

The United States said on Sunday that it officially withdrew from the treaty, in yet another departure from a major international arms control agreement.

The treaty, which became effective in 2002, allows its 34 State Parties to conduct short-notice, unarmed reconnaissance flights over the others' entire territories to collect data on military forces and activities.