WASHINGTON, April 16 (Xinhua) -- U.S. Acting Secretary of Defense Patrick Shanahan on Tuesday met with Turkish Defense Minister Hulusi Akar over mutual interests, said the Pentagon.

Shanahan and his Turkish counterpart discussed "the importance of U.S.-Turkish cooperation bilaterally and as NATO Allies in achieving mutual security and economic prosperity for both countries and the region", according to a Pentagon statement.

The statement also emphasized that the two defense chiefs met as strategic partners and "focused their discussion on interests, rather than positions," but without providing further details.

The United States is in a feud with Turkey over the latter's purchase of Russian S-400 air defense system.

On April 3, U.S. Vice President Mike Pence warned Turkey against purchasing the S-400 air defense system from Russia, despite Ankara's firm stance on the deal. "The S-400 deal is a done deal and we will not step back from this," Turkish Foreign Minister Mevlut Cavusoglu said.

During a congressional hearing in March, General Curtis Scaparrotti, head of U.S. European Command, suggested that the United States should cut the sale of F-35 fighters to Turkey if Ankara adopts S-400 air defense system.

Pentagon announced early this month that it halted "deliveries and activities" related to Turkey's procurement of the F-35 fighter jets program if Ankara insisted on the S-400 deal.

"If we don't have F-35, I need to take the plane elsewhere," Cavusoglu said last week, adding that Russian fighter jets -- Su-34 and Su-57 -- could be alternatives to meet Turkey's demand.

Kremlin Spokesman Dmitry Peskov this past Sunday spoke highly of Turkey's tough stance on the purchase of Russian S-400 system despite U.S. opposition.