NATO Secretary General Jens Stoltenberg speaks during a media conference at NATO headquarters in Brussels.

NATO is ready to send troops to Turkey to defend its ally against threats on its southern flank, the head of the U.S.-led alliance said on Thursday after violations of Turkish airspace by Russia jets conducting air strikes in Syria.

“NATO is ready and able to defend all allies, including Turkey against any threats,” Jens Stoltenberg told reporters before a meeting of NATO defence ministers in Brussels that will be dominated by the Syria crisis.

“NATO has already responded by increasing our capacity, our ability, our preparedness to deploy forces including to the south, including in Turkey,” he said, noting that Russia’s air and cruise missile strikes were “reasons for concern”.

He also said no decision had been taken on NATO troop levels in Afghanistan.

The North Atlantic Treaty Organization was formed in Washington, D.C. in 1949, comprising the 12 nations of the Atlantic Pact together with Greece, Turkey, and the Federal Republic of Germany, for the purpose of collective defense against aggression.