Turkey reopened the airspace around Incirlik Air Base on Sunday, allowing the U.S. to restart strike missions targeting the Islamic State terror group, as the alliance between the two nations showed signs of serious strain.

Pentagon Press Secretary Peter Cook confirmed that power had been cut to the air base in southern Turkey, near the Syria border.

“U.S. facilities at Incirlik are still operating on internal power sources, but we hope to restore commercial power soon. Base operations have not been affected,” Cook said in a statement.

Meanwhile, U.S. Secretary of State John Kerry spoke to his Turkish counterpart, Mevlut Cavosoglu, for the second time in as many days following the failed coup, which left at least 265 people dead and 1,400 wounded.