Last month, the U.S. formally suspended its obligations under the 1987 INF treaty that bans all land-based cruise and ballistic missiles with a range of 500 to 5,500 kilometers (310 to 3,410 miles), setting the stage for the treaty to terminate in six months. Russia, which has denied any breaches, has followed suit.
"NATO does not want a new cold war, we don't want a new arms race and we call on Russia to come back into compliance with the INF Treaty," Stoltenberg said after talks with Bulgarian Prime Minister Boyko Borissov in Sofia.
"These new Russian missiles are nuclear capable, they can reach European cities, they are hard to detect, and they have little warning time so they reduce the threshold for any potential use of nuclear weapons in an armed conflict and therefore it's important that we continue to call on Russia to come back into compliance," Stoltenberg said.
He added that at the same time NATO needs to be prepared for a world without the INF Treaty and with more Russian missiles. The intermediate-range weapons were seen as particularly destabilizing as they take shorter time to reach their targets compared to the intercontinental ballistic missiles. That would leave practically no time for decision-makers, raising the likelihood of a global nuclear conflict over a false launch warning.
Russian President Vladimir Putin sternly warned the U.S. against deploying new missiles in Europe, saying in his state-of-the-nation speech last month that Moscow will retaliate by fielding new weapons that will take just as little time to reach their targets.
Stoltenberg, who is in Bulgaria for the 15th anniversary of the country joining NATO, thanked the Balkan country for being "a committed and highly valued ally in the alliance." He outpointed Bulgaria's strategic role in the Black Sea region, and the country's contribution to NATO missions in Afghanistan, Kosovo and Iraq.
Vladimir Isachenkov in Moscow contributed to this report.