President Trump announced on Wednesday that the United States will pull out from the major 35-nation arms control treaty that allows nations to operate reconnaissance flights over other territories—a critical agreement for building trust and maintaining peace between countries. The official withdrawal from the post-Cold War ‘Open Skies’ agreement will reportedly happen in six months in accordance with the treaty’s exit policy. The move was prompted by several instances where Russia refused to comply with the pact, which poses a threat to the U.S. military and cybersecurity, The New York Times reports.

It will be the third major arms control agreement Trump has chosen to exit—after the Iran nuclear deal and the Intermediate Nuclear Forces treaty—and reportedly indicates that he may also choose to pull out from the U.S.-Russia nuclear pact START. “During the course of this review it has become abundantly clear that it is no longer in America’s interests to remain a party to the Open Skies treaty,” a top U.S. official told Reuters.