"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 yesterday, as he travelled to a military headquarters in Florida.
"We are doing good work with them, military to military," he stressed.
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The diplomatic spat erupted last week, when Turkey arrested a Turkish employee of the American consulate on suspicion of having 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 by telephone with US Secretary of State Rex Tillerson yesterday 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 spokesperson Heather Nauert said.
On Tuesday, a Pentagon spokesperson 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 air strikes against the Islamic State group in neighbouring Syria and Iraq.