This May 22, 2020 AFP graphic shows the 35 signatories to the Treaty on Open Skies.

WASHINGTON/BERLIN - Germany said it "deeply regrets" the United States' withdrawal from the Opens Skies treaty and remains committed to the international arms control agreement, while Russia said it will seek firm guarantees that the states remaining in the treaty fulfill their obligations.

"We deeply regret that the U.S. decided to take this step and is now doing it. Our stance on the treaty has not changed: we see it as an important part of the arms control architecture," Foreign Minister Heiko Maas said in a statement on Sunday.

Maas said that Germany is committed to efforts to overhaul the treaty so as to improve its role in confidence building between its members.

Noting that the country sees the the Treaty on Open Skies as "an important part of the arms control architecture," Germany reiterated its stance on the treaty remained unchanged, while Russia said it would seek guarantees that the remaining signatories in the treaty fulfill their obligations

The US announced on Sunday that it has officially withdrawn from the Open Skies treaty.

"Today marks six months since the United States submitted our notice of withdrawal from the Treaty on Open Skies," National Security Adviser Robert O'Brien said in a tweet.

The Trump administration submitted the notice of its decision to withdraw from the treaty in May, and the Sunday announcement marked the end of a six-month notification process.

READ MORE: US to exit Open Skies treaty, citing Russian violations

The treaty, which became effective in 2002, allows its 35 State Parties to conduct short-notice, unarmed reconnaissance flights over the others' entire territories to collect data on military forces and activities.

The United States and Russia have blamed each other for noncompliance with the treaty. Washington and Moscow have each put a few limits on flights over their territories - Hawaii and some other US bases have been off-limits, as has Kaliningrad, among others, according to media reports.

The treaty is aimed at building confidence and familiarity among State Parties through their participation in the overflights. By 2019, more than 1,500 Open Skies flights have been conducted since the deal entered into force, according to media reports.

The treaty, which became effective in 2002, allows the State Parties to conduct short-notice, unarmed reconnaissance flights over the others' entire territories to collect data on military forces and activities

Some experts noted that a unilateral US exit from the treaty would undermine US commitment to its NATO allies.

ALSO READ: Russia: US exit from Open Skies undermines global security

"After withdrawing from the Treaty on Open Skies, the U.S. side expects that its allies, on the one hand, will hinder Russian observation flights above U.S. military facilities in Europe, and, on the other hand, share with Washington their photographic materials of Russian territory," the Russian Foreign Ministry said in a statement on Sunday.

"Of course, this is unacceptable for Russia," it added.

"We will seek firm guarantees that the states remaining in the Treaty on Open Skies will fulfill their obligations, firstly, on ensuring the possibility of observing their entire territory and, secondly, on ensuring that the materials of observation flights will not be transferred to third countries that are not participants of the treaty," it said.