Russia has secretly deployed a new cruise missile despite complaints from American officials that it violates a landmark arms control treaty that helped seal the end of the Cold War, administration officials say….

The ground-launched cruise missile at the center of American concerns is one that the Obama administration said in 2014 had been tested in violation of a 1987 treaty that bans American and Russian intermediate-range missiles based on land.

The Obama administration had sought to persuade the Russians to correct the violation while the missile was still in the test phase. Instead, the Russians have moved ahead with the system, deploying a fully operational unit.

Administration officials said the Russians now have two battalions of the prohibited cruise missile. One is still located at Russia’s missile test site at Kapustin Yar in the country’s southeast.

The other was shifted in December from that test site to an operational base elsewhere in the country, according to a senior official who did not provide further details and requested anonymity to discuss recent intelligence reports about the missile….

The deployment of the system could also increase the military threat to NATO nations, which potentially would be one of the principal targets. Defense Secretary Jim Mattis is scheduled to meet with allied defense ministers in Brussels on Wednesday.

Before he left his post last year as the NATO commander and retired from the military, Gen. Philip M. Breedlove warned that deployment of the cruise missile would be a militarily significant development that “can’t go unanswered.”

Image: Russian President Vladimir Putin, Jan. 17, 2017 (photo: Office of the President of Russia)