Illustrated photo (Source: Tass)

 Ryabkov said that if the US does not reconsider its viewpoint on the Open Sky Treaty before the end of May, Russia will deliver notes to the related parties announcing its withdrawal from the Treaty. Russia has not seen any US interest in implementing the Treaty, only interest in delaying the issue.
Last Wednesday, a US State Department spokesperson  said Washington urges Moscow to get back into compliance with the Treaty. On February 3, State Department spokesperson Ned Price said the US is considering returning to the Treaty and will make an official decision at the appropriate time. 
The Open Sky Treaty was signed in 1992 and entered into force in 2002, with the participation of 35 countries. The Treaty permits each party to conduct short-notice, unarmed, reconnaissance flights over the others' entire territories to collect data on military forces and activities.