The Associated Press subsequently reported that the flights had already begun.

The flights are a further acknowledgment that the group also known as Islamic State (IS) is a threat beyond Iraq, and the operations would inform any decision to conduct airstrikes near the ISIS haven of Raqqa in eastern Syria.

Significantly, the missions will be carried out without coordination with or approval from the regime of Syrian President Bashar al-Assad. Officials noted that regime "air-defense systems in eastern Syria won't pose a threat because sensors are either sparsely located or inoperable," WSJ reports.

ISIS militants have consolidated their grip on northeast Syria by capturing the Tabqa air base and other remaining regime-held military bases in the Raqqa province.