"We’re going to try to give opportunities and power to ... particularly Sunni Arabs in Syria who want to re-seize their territory back from ISIL, especially Raqqa," Carter said after defense talks in Brussels, Reuters reports.

Carter said it had also promised to resume participating in the U.S.-led air campaign against Islamic State. He received a similar assurance from Saudi Arabia on Thursday.

"We’re not looking to substitute for them [the Syrian rebels], any more than we’re looking to substitute for the Iraqi forces. But we are looking to enable them strongly and help them organize themselves," Carter said.

He said the United Arab Emirates could also play an important role in Iraq, helping train local forces, including Kurdish peshmerga fighters.

Read alsoAl Arabiya: Saudi's decision to send troops in Syria 'final'Such a plan would meet stiff resistance from NATO member Turkey. On Wednesday, Turkish President Tayyip Erdogan upbraided the United States for its support of Kurdish fighters.

Turkey has fought militants from the Kurdistan Workers Party (PKK), who seek autonomy for mainly Kurdish southeast Turkey, for three decades.