By Dasha Afanasieva and Phil Stewart
ISTANBUL/WASHINGTON (Reuters) - The U.S. military has started training Syrian fighters to combat Islamic State militants, officials said on Thursday, adding the program had begun in Jordan and would soon launch in Turkey.
The U.S. plan to train and arm a force that is expected to eventually total more than 15,000 troops is a major test of President Barack Obama's strategy in Syria, which critics say is too limited to influence events.
The Pentagon declined comment. But U.S. and Middle Eastern sources, speaking to Reuters on condition of anonymity, confirmed that training had commenced.
A Jordanian government spokesman said it started there several days ago.
No further details were immediately available.
The program faces deep skepticism, including from rebels fighting inside Syria. Some rebel leaders say the force risks sowing divisions and cannot succeed without directly targeting Syrian government forces.
The Obama administration says the program aims only to target Islamic State forces, since the United States is not at a war with Syria.
But critics, including in the U.S. Congress, say that theoretical limitation is unlikely to withstand the realities of Syria's messy civil war.
U.S.-trained Syrian fighters, they say, are likely to come in contact with Syrian President Bashar al-Assad's forces eventually. And the priority of key U.S. allies in the region, including Saudi Arabia and Turkey, is to topple Assad.
It was unclear whether Obama had yet decided how extensively and under what circumstances Washington might support the force militarily inside Syria - a commitment that would risk the very entanglement in the war that Obama has sought to avoid.
U.S. officials have previously told Reuters it was possible training would begin without that clarity.
Part of the U.S. strategy, according to Obama administration documents seen by Reuters, is to pressure Assad by steadily increasing the opposition's prowess and territory under its control.
Proponents of the U.S. military program note Assad is already facing growing pressure after government forces endured a series of recent setbacks on the battlefield and Islamist fighters edge closer to Assad's stronghold in the coastal areas.
(Additional reporting by Suleiman Al-Khalidi in Amman; Editing by Will Dunham, Doina Chiacu and Bernadette Baum)