WATCH: Pentagon cautions Turkey on strikes in Syria

Pentagon Spokesman Brig. Gen. Pat Ryder said U.S. Defense Secretary Lloyd Austin spoke with his Turkish counterpart and expressed strong opposition to Turkish military action in Syria following last month’s bomb attack in Istanbul.

Watch the briefing in the player above.

Turkish authorities say the deadly bombing in Istanbul on November 13th was a terrorist attack and they blame it on Kurdish separatists.

“We certainly do recognize Turkey’s valid security concerns when it comes to protecting their people inside their borders,” Ryder said.

“The focus here is on preventing a destabilizing situation which would put ISIS in an ability to reconstitute,” he said. “And no one wants to go back to what we saw in 2014 with a terrorist group running amok and taking large swaths of swaths of land with thousands and thousands of people killed.”

WATCH: Turkey attacks Syrian Kurds, the U.S. partner in fight against ISIS

U.S. and Kurdish military officials say Turkish airstrikes and a threatened ground invasion in northern Syria are impacting their joint operations against the Islamic State extremist group.

Ryder previously told reporters that the U.S. has cut back on the number of “partnered patrols” it is carrying out alongside the SDF in northern Syria.Thursday, he said U.S. troops are safe in their mission.

“But again, this demonstrates why it’s very important that while this important defeat ISIS mission continues, that we are able to work together and communicate to ensure that there’s continued stability in the region,” he said.