"At the Open Skies Consultative Commission in Vienna, Austria, on September 26, the United States announced we would implement Treaty-compliant measures in response to Russia's noncompliance with the Open Skies Treaty," the spokesperson said. "Our measures are intended to encourage Russia to engage with us more constructively about our concerns."
Earlier in the day, Russian Foreign Ministry spokeswoman Maria Zakharova said that Russia had notified the US of rejecting several agreements within the Open Skies Treaty.
The same source said that such a decision was made as a mirror response to US-announced measures that include intentions of the United States to close the airspace over Alaska and Hawaii to Russian observers and limit the range of flights.
The Treaty on Open Skies entered into force on January 1, 2002, and 34 states are party to the agreement. It establishes a program of unarmed aerial surveillance flights over the entire territory of its participants.