The United States will send over 400 troops to train moderate Syrian rebels battling militants of the Islamic State group and al Qaeda, a Pentagon spokesperson said late on Thursday, according to media reports. The troops, along with hundreds of U.S. support personnel, will reportedly begin training the rebels as early as March.

The training of the Syrian rebels will be carried out in three countries -- Turkey, Qatar and Saudi Arabia.

The military personnel will also be assisted by troops from those countries that are part of the U.S.-led coalition carrying out airstrikes in Syria, Defense One reported on Thursday. However, the U.S. military has still not disclosed which countries would be contributing forces for the training operation, which has a target of training over 5,000 Syrian rebels every year for the next three years, according to a Reuters report. The aim of the program is to train at least 15,000 rebels to reclaim the territory captured by the Islamic State group.

Since June last year, moderate rebels have been battling not only ISIS, which has seized large swathes of territory in Syria and around one-third of Iraq, but also militants of the Jabhat al-Nusra -- the Syrian affiliate of al Qaeda -- and troops loyal to Syrian President Bashar Assad. Although the rebels are being assisted by airstrikes carried out by the U.S.-led coalition, the offensive has failed to halt the advance of ISIS in Syria’s northeastern regions, according to a recent report by The Wall Street Journal.

The news of the planned troop deployment comes just days after officials of the U.S. Central Command met the Syrian opposition in Istanbul, Turkey, to discuss the training of Syrian rebels.

“These meetings provided an important opportunity to introduce and discuss the U.S. train and equip program with members of the moderate political and armed opposition and to gain a better understanding of conditions on the ground in Syria,” CentCom had said, in a statement released, on Wednesday.