ANKARA, Turkey — US Defense Secretary Ash Carter visited Turkey on Dec. 15 in efforts to devise new strategies to fight the Islamic State of Iraq and the Levant (ISIL) in Syria and Iraq.

"We want Turkish forces to join in the air and on the ground as appropriate," Carter told reporters on Dec. 15.

He said the US was urging Turkey to introduce better controls over its 900-kilometer border with Syria in order to block the flow of foreign ISIL fighters into Syria.

Carter also said that he would be asking ask military commanders and officials to suggest new tactics that can be used to attack ISIL, and to identify new contributions coalition partners could make to accelerate the destruction of the jihadist group.

From the Turkish point of view, Carter's visit comes at a time when the Turkish military has been involuntarily refraining refrained from joining the US-led coalition airstrikes against ISIL.

After two Turkish F-16 fighters intercepted and shot down a Russian SU-24 aircraft on Nov. 24 along Turkey's border with Syria Nov. 24, citing a brief airspace violation, Russia threatened Turkey to retaliate through means other than commercial sanctions only.

Since then, Russia has reinforced its military deployments in the eastern Mediterranean and inside Syria, including stationing S-400 air and anti-missile defense systems, threatening any Turkish airplane over Syrian skies.

Since then t The Turkish air force has suspended airstrikes against ISIL strongholds in Syria ever since.