Democratic lawmakers and national security experts have excoriated the White House's abandonment of the Open Skies Treaty.
The State Department announced it would submit its notice of withdrawal, which starts a 6-month countdown.
According to Business Insider, the 34-country treaty includes Russia, Ukraine, Canada, the Netherlands, and Norway.
These countries can conduct short-notice observational flights over other signatories to verify the status of each other's military forces.