Turkish Defense Minister Hulusi Akar and U.S. counterpart James Mattis spoke over the phone and discussed bilateral defense deals, Syria and counterterrorism, Reuters reported on Tuesday.

The report cited Turkish broadcasters and the state news agency, which did not cite their source.

Relations between the two countries have soured over a series of issues, but most recently over the trial of U.S. pastor Andrew Brunson on terrorism charges.

Brunson, who has been detained in the country for more than year, is accused of working with Fethullah Gulen, an Islamic cleric who Turkish President Recep Tayyip Erdogan claims orchestrated a failed coup in 2016.

Last week, the Trump administration imposed sanctions on individuals and institutions in response to the trial of Brunson.

The Turkish Foreign Ministry has vowed to "retaliate" against the U.S. sanctions, calling the American move a "hostile stance".

On Monday, however, it was reported that a delegation of Turkish officials will head to Washington to discuss the row between the two countries.