Syrian Democratic Forces and U.S. troops are seen during a patrol near Turkish border in Hasakah, Syria, Nov. 4, 2018. (REUTERS Photo)

WASHINGTON, March 7 (Xinhua) -- General Joseph Votel, head of the U.S. Central Command, said on Thursday that U.S military has not fixed a specific date to withdraw forces from Syria.

"We don't withdraw in a manner that increases the risk to our forces ... There is not pressure on me to meet a specific date at this particular time," Votel said during a House Armed Services Committee hearing.

Votel, who oversees U.S. military in the Middle East, noted in the hearing that the operation against the Islamic State (IS) is far from over. "Reduction of the physical caliphate is a monumental military accomplishment -- but the fight against ISIS and violent extremism is far from over and our mission remains the same."

The U.S.-backed Syrian Democratic Forces (SDF) said that they would launch a final assault on the IS-held enclave of Baghouz in eastern Syria after all civilians have been evacuated, according to media reports.

A spokesperson of SDF said on twitter Tuesday that 3,500 people had been evacuated from the enclave and 500 IS fighters surrendered.

Votel revealed that the IS militants evacuated from the remaining IS-held territories were largely "unrepentant, unbroken and radicalized," adding that the IS made a calculated decision "to preserve the safety of their families and preservation of their capabilities... and waiting for the right time to resurge."

"In my view this is a serious generational problem that, if not handled properly, will sow the seeds of future violent extremism," he said.

Declaring victory over the IS, President Donald Trump announced in December the withdrawal of U.S. troops from Syria, leading to the resignation of then Secretary of Defense James Mattis and wide opposition from home and abroad.

Last month, Trump announced a small fraction of U.S. forces would remain in Syria with troops from other countries. Citing a senior administration official, NBC News later reported that the U.S. military would leave about 400 troops in two different regions of Syria.

According to the official, half of them would join the multinational force of roughly 800 to 1,500 troops deployed in northeastern Syria to maintain a buffer between Turkey and U.S.-backed Kurdish forces. The rest 200 troops would stay at its base in al-Tanf, near the Syrian border with Iraq and Jordan.

Currently, there are about 2,000 U.S. troops deployed in Syria.