The Latest: US says fight for Raqqa will be 'difficult'

BEIRUT – The Latest on the conflict in Syria (all times local):

2 p.m.

A U.S. military official says the offensive against the Islamic State group's de facto capital, Raqqa "will be long and difficult."

Lt. Gen. Steve Townsend, the top U.S. commander in Iraq, says the assault by the Syrian Democratic Forces will deliver a decisive blow to the idea of IS "as a physical caliphate."

The Kurdish-led force launched an offensive to capture Raqqa on Tuesday. Iraqi forces have captured much of Mosul, the largest city held by extremists.

Townsend said "it's hard to convince new recruits that ISIS is a winning cause when they just lost their twin 'capitals' in both Iraq and Syria," referring to IS by another acronym.

He said U.S.-led coalition forces will continue to support the SDF in Raqqa, providing equipment, training, Intelligence and logistics as well as precision firepower.

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1:45 p.m.

Turkey's prime minister says his country will respond if an offensive by U.S.-backed Syrian forces to recapture the Islamic State-held city of Raqqa poses a security threat to Turkey.

In an address to legislators from his ruling party, Binali Yildirim again criticized the United States for launching the Raqqa offensive with the Kurdish-led Syrian Democratic Forces.

NATO member Turkey considers the Kurdish fighters within the SDF terrorists because of their links to outlawed Kurdish rebels in Turkey and had opposed their involvement in the operation.

Yildirim said: "To support terror organizations does not suit (our) alliance."

He added: "We will immediately give the necessary response if we come across a situation in Raqqa or any other point in the region that threatens our security."

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11:45 a.m.

A U.S.-backed Syrian force says it has begun an offensive to capture the northern city of Raqqa, the de facto capital of the Islamic State group.

Talal Sillo, a spokesman for the Kurdish-led Syrian Democratic Forces, told reporters Tuesday that operations have begun in coordination with the U.S.-led coalition.

SDF fighters began advancing toward Raqqa in November, capturing wide areas from the extremists. Last week, they reached the northern and eastern gates of the city.

Raqqa is currently surrounded from the east, north and west, and opposition activists have reported intense shelling on the city since Monday night, which killed at least 12 people.

The battle is likely to be long and bloody, and the extremists are not expected to give up easily.

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10:45 a.m.

Syria's state news agency and an opposition monitoring group say airstrikes on the northern city of Raqqa, the de facto capital of the Islamic State group, have killed at least 12 people.

State news agency SANA reported on Tuesday that the airstrikes by the U.S.-led coalition killed 12, including women and children. It says the families were fleeing the city in boats across the Euphrates River ahead of an expected all-out attack by the Kurdish-led Syrian Democratic Forces.

The Britain-based Syrian Observatory for Human Rights said 21 people were killed in the Monday night airstrikes. It said they were likely carried out by the U.S.-led coalition.

The airstrikes have intensified in recent weeks as SDF fighters have reached the outskirts of the city.