NATO Secretary-General Jens Stoltenberg has said the Western military alliance must be prepared if Russia ignores calls to return to compliance with the Intermediate-Range Nuclear Forces (INF) Treaty, a cornerstone of arms control for decades.

In an interview with RFE/RL’s Bulgarian Service on March 1, Stoltenberg said NATO needed to start "planning for a situation without the INF Treaty, with more Russian missiles."

Stoltenberg was in Bulgaria for the 15th anniversary of the country joining NATO. He earlier held talks with Bulgarian Prime Minister Boyko Borissov.

Last month, Washington 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.

This came after Washington and NATO repeatedly accused Moscow of violating the accord by developing the 9M729 cruise missile, also known as the SSC-8.

Russia, which has denied any breaches, has also announced it is withdrawing from the INF Treaty.

Relations between the West and Russia are also strained over Russia’s actions in Ukraine and Syria as well as its alleged interference in elections in the United States and elsewhere.

'Dual-Track Approach'

Stoltenberg said NATO was taking what he called a "dual-track approach -- deterrence, defense and dialogue," with Russia.

“Russia is our neighbor, Russia is there to stay, and we need to work for improving relations with Russia and strive for reducing the tensions. So, we strongly believe that to be united, to be firm [as NATO] is a platform for also engaging in a political dialogue with Russia to reduce tensions," Stoltenberg told RFE/RL.

Stoltenberg also said NATO was bolstering its presence in the Black Sea and Baltic regions.

“We have done that because we see significant Russian military buildup, we see Russia investing heavily in a wide range of weapon systems, including nuclear weapons, and we are seeing the fact that Russia has used military force against the neighbor illegally annexing Crimea [from Ukraine] and then destabilizing eastern Ukraine."

In his state-of-the-nation speech last month, Russian President Vladimir Putin said if the United States deployed new missiles in Europe, Moscow would retaliate by fielding new weapons that will take just as little time to reach their targets.