Turkey's foreign minister says Turkey and the United States have agreed in "principle" to provide air protection to Syrian rebels being trained and equipped to fight Islamic State rebels, once they enter the Syrian territory to start battle.

The two countries agreed in February to train and equip Syrians under the $500 million U.S. program.

Mevlut Cavusoglu told Daily Sabah newspaper in comments published Monday: "They have to be supported via air. If you do not protect them or provide air support, what is the point?"

He did not provide details on the air cover.

U.S. officials have said the aim is to train 5,000 Syrians a year for three years at a base in the central Turkish city of Kirsehir and at sites in Saudi Arabia and Qatar.