MOSCOW (AP) — The Russian parliament's lower house voted Wednesday to withdraw from an international treaty allowing surveillance flights over military facilities following the U.S. departure from the pact.

The Russian exit from the Open Skies Treaty is yet to be endorsed by the upper house of parliament and needs to be signed by President Vladimir Putin to take effect. Moscow has signaled its readiness to reverse the withdrawal procedure and stay in the treaty if the U.S. returns to the agreement.

The Open Skies Treaty was intended to build trust between Russia and the West by allowing the accord’s more than three dozen signatories to conduct reconnaissance flights over each other’s territories to collect information about military forces and activities. More than 1,500 flights have been conducted under the treaty since it took effect in 2002, aimed at fostering transparency about military activity and helping monitor arms control and other agreements.

U.S. President Donald Trump pulled out of the pact, arguing that Russian violations made it untenable for Washington to remain a party. The U.S. completed its withdrawal from the pact in November.

Russia has insisted that the restrictions on observation flights it imposed in the past were permissible by the treaty and noted that the U.S. imposed more sweeping restrictions on observation flights over Alaska.