US and Turkish military relations not affected by diplomatic row, says Mattis

"We maintain a very close collaboration, very close communication, the military-to-military interaction and integration has not been affected by this," Mattis told reporters as he travelled to a military headquarters in Florida.

"We are doing good work with them, military to military," he stressed.

The diplomatic spat erupted last week when Turkey arrested a Turkish employee of the American consulate on suspicion of links to the group blamed for last year's failed coup.

In response, the United States stopped issuing non-immigrant visas from its missions in Turkey, prompting Turkish missions in the United States to hit back with a tit-for-tat move.

Turkish Foreign Minister Mevlut Cavusoglu spoke with US Secretary of State Rex Tillerson by telephone on Wednesday to discuss the reciprocal suspension of visa services, their first talks since the eruption of one of the worst crises between Washington and Ankara in years.

During the conversation, Tillerson said Turkey needed to present evidence for the accusations against the consulate employee, State Department spokeswoman Heather Nauert said.

On Tuesday, a Pentagon spokesman said the row had not affected NATO or US military ties with Turkey.

The United States relies heavily on an air base at Incirlik in southern Turkey to launch airstrikes against the Islamic State group in neighbouring Syria and Iraq.