US Army Special Forces have been covertly aiding in Saudi Arabia’s war against Yemen, New York Times reported.

Citing information provided by US officials and European diplomats, the Times reported Thursday that about a dozen Green Berets were deployed to Saudi Arabia’s border with Yemen in December, a month after the Houthi revolutionaries fired a Burkan-2 ballistic missile at Riyadh’s international airport.

Saudi Arabia claimed to have intercepted the November attack with its US-built MIM-104F Patriot missile defense system, but analysts have cast doubt on this official version of events.

Saudi Arabia’s Crown Prince and Defense Minister Mohammed bin Salman reportedly reached out to the U.S. for help in locating and destroying Houthi missile launch sites shortly after, opening what may be a new shadowy front for the Pentagon’s operations in the Middle East.

Part of their mission is to also train Saudi troops on how best to defend their border with Yemen, according to the daily.

The Green Beret operation, which has not been previously disclosed appears to contradict Pentagon statements that American military assistance to the Saudi-led campaign in Yemen is limited to aircraft refueling, logistics and general intelligence sharing.

Meanwhile, the Times added that there was no indication that the American commandos have crossed into Yemen as part of the secretive mission.