(Reuters) - The United States and Turkey have reached a tentative agreement to train and equip moderate Syrian opposition fighters and expect to sign the pact soon, U.S. and Turkish officials said on Tuesday with Ankara predicting a signing in days.

The U.S. military has said it is planning to send more than 400 troops, including special operations forces, to train Syrian moderates at sites outside Syria as part of the fight against the Islamic State.

U.S. officials have said they plan to train about 5,000 Syrian fighters a year for three years under the plan. Saudi Arabia and Qatar, as well as Turkey, have publicly offered to host training sites.

Turkey hopes the training will also bolster the weakened and divided Syrian opposition in their struggle against Syrian President Bashar al-Assad.

"Negotiations have been concluded and an agreement text will be signed with the U.S. regarding the training of the Free Syrian Army in the coming period," Turkish foreign ministry spokesman Tanju Bilgic said.

"We will share all the technical details ... when the text is signed, but it is anticipated that this will happen in the coming days," he told reporters in Ankara.

In Washington, State Department spokeswoman Jen Psaki confirmed an agreement with Ankara in principle.

"As we have announced before, Turkey has agreed to be one of the regional hosts for the train-and-equip program for moderate Syrian opposition forces. We expect to conclude and sign the agreement with Turkey soon," Psaki told reporters.

The Free Syrian Army is seen by Turkey as a key actor in Syria's kaleidoscopic conflict, but the group has been riven by divisions and suffered setbacks at the hands of government forces and other rebel factions.

A deal between Ankara and Washington would be a positive development between the two longstanding allies, despite strains over Middle Eastern policy. Turkey wants Assad's departure to be the focus in Syria, while Washington's priority remains battling the Islamic State insurgents.