British Foreign Secretary David Miliband said on Thursday that Russia's decision to suspend a treaty which puts clear limits on the stationing of troops and heavy weapons across Europe was "unjustified".
In a written statement to parliament, Miliband added that he "regrets the unilateral decision" by Moscow to freeze its compliance with the Conventional Forces in Europe (CFE) treaty, signed in 1990.
Experts say that the agreement, whose suspension means Russia can deploy its troops anywhere without telling NATO, helped facilitate the end of the Cold War.
"This Russian decision is unjustified," Miliband wrote.
"The UK (United Kingdom), along with NATO allies, has made clear our commitment to ratify as quickly as possible the adoption of the CFE treaty, which would provide the basis for addressing most of Russia's concerns about the current CFE regime."
He added that European security is "not fundamentally or immediately threatened by this Russian action" and pledged to consult with allies in NATO on a joint response.
NATO has already said it deeply regrets Russia's suspension which took effect earlier this week, while the United States has also condemned the move.