A top leader in the US military has refused to mince his words in a violent threat to terror group Isis, telling its remaining fighters that should they refuse to surrender the US is not afraid of "beating them to death with entrenching tools".

Army Command Sgt. Maj. John Troxell, a senior adviser to the chairman on the Joint Chiefs of Staff, posted a statement on social media after making similar comments during a recent tour with the United Service Organisations.

"Isis needs to understand that the Joint Force is on orders to annihilate them," he wrote (via CNN)

"So, they have two options should they decide to come up against the United States, our allies and partners: surrender or die!

"If they choose not to surrender, then we will kill them with extreme prejudice, whether that be through security force assistance, by dropping bombs on them, shooting them in the face, or beating them to death with our entrenching tools."

The post ends with the hashtag #ISIS_SurrenderOrDie.

Isis suffered huge losses in 2017, losing territory in Syria and being all but wiped out in Iraq.

Last month The Pentagon stated that the US military would remain involved in the fight against Isis in Syria until the areas reclaimed from the terrorist group are stable. Troops will be withdrawn when "conditions" on the ground allow it.