U.S. Defense Secretary Ashton B. Carter, right, and his British counterpart, Michael Fallon, talk prior before a NATO summit in Warsaw on Saturday. The summit set out plans for open-ended NATO deployments to Eastern Europe as a bulwark against Moscow’s forces. (Alik Keplicz/AP)

Russian diplomats on Wednesday offered a new plan to improve safety in the air over the Baltics in a rare meeting with NATO ambassadors, a small but significant step to ease tensions amid a troop buildup on both sides of the bristling NATO-­Russia border.

The proposal would commit Russian and all other planes flying over the Baltic Sea to switch on their transponders, a step that helps civil aviation authorities track flights and avoid near-misses. NATO allies have complained that Russian warplanes regularly fly in the region without the ability to be tracked by civilian aircraft.

The meeting of the NATO-Russia Council was only the second such conclave since Russia’s 2014 annexation of Crimea plunged relations to Cold War lows. It also came just days after a landmark NATO summit in Warsaw set out plans for open-ended deployments to Eastern Europe as a bulwark against Moscow’s forces, sparking bitter Kremlin recriminations.

The plans to deploy about 4,000 NATO troops to Estonia, Latvia, Lithuania and Poland are meant to alleviate fears in those nations that they could be next after Russia intervened in Ukraine. Russia has reacted to the NATO plans with fury, saying they create a security threat on its borders.

Both sides have dug in after relations soured in 2014. In the Baltics, Russian warplanes have buzzed Western aircraft and ships in incidents that U.S. military officials said could lead to accidents and dangerous escalations.

In an apparent bid to ease some of the tensions, Alexander Grushko, Russia’s ambassador to NATO, said Russia had made the proposal during the meeting.

“We made it very clear that we are ready to fly with transponders on along certain trajectories of flight, and we do hope that NATO countries are ready to discuss this proposal and to do the same on a reciprocal basis,” he said. 

NATO requires aircraft flown under its direct command to fly with their transponders on, but those flown separately by NATO allies do not always do the same. The Russian proposal was welcomed by NATO officials, who said they would study it. The plan may help foster military-to-military discussions, a step NATO officials have said would also improve safety.

But Grushko condemned most other aspects of NATO’s operations in Europe.

NATO Secretary General Jens Stoltenberg was similarly cautious in his assessment of Wednesday’s talks.

“There was not a meeting of minds today,” Stoltenberg said. But he said it was useful to exchange views.

He said the Kremlin needs to provide broader reassurances that it will fly more carefully in the region.

NATO officials have grown concerned about a Russian military buildup in Kaliningrad, a Russian enclave on the Baltic Sea that borders Poland and Lithuania and is the headquarters of Russia’s powerful Baltic Fleet. Since 2014, the Russian military has bolstered antiaircraft defenses, leading to a bubble of airspace control that could deny Western aviation access to much of the Baltics in case of war.

Russian officials are deeply concerned by the U.S.-led construction of a NATO-controlled missile defense system in Europe, which the Kremlin says could disrupt its strategic nuclear deterrent.

NATO officials insist that the system is intended to defend against Iran and does not have the technical capabilities to defend against Russian missiles.

Secretary of State John F. Kerry is expected to meet Thursday with Russian President Vladi­mir Putin and Foreign Minister Sergei Lavrov in Moscow to discuss NATO, terrorism and the Syrian conflict.  Kerry plans to propose coordinating Russian and American airstrikes in Syria against Jabhat al-Nusra, al-Qaeda’s affiliate in Syria, and the Islamic State .

Kerry sees the effort as a chance to reduce violence in Syria. However, a growing number of defense, intelligence and diplomatic officials object, questioning the long-term value of cooperating with Russia in Syria.

Andrew Roth in Moscow contributed to this report.