AIN ISSA, Syria (Reuters) - The U.S.-backed Syrian Democratic Forces will respond strongly to any Turkish attack but is pressing diplomatic efforts to deter an assault, its commander-in-chief said on Thursday.

Mazloum Kobani, SDF commander in chief is pictured during an interview with Reuters in Ain Issa, Syria, December 13, 2018. REUTERS/Rodi Said

In a rare interview, Mazloum Kobani told Reuters that Washington had made “serious attempts” to prevent a Turkish offensive against Kurdish fighters who control a swathe of northern Syria at the Turkish border, but the United States should ramp up its efforts further.

The SDF, which is spearheaded by the Kurdish YPG militia, has been at the heart of the U.S.-backed fight against Islamic State. It has seized vast territory from the jihadists with the help of U.S. warplanes and special forces.

SDF commander-in-chief Kobani warned that a Turkish assault would tie up YPG fighters who are currently fighting Islamic State remnants in eastern Syria, allowing the jihadists to spread again.

“We are ready for any attack and will respond strongly...within our areas,” said Kobani, a founder of the SDF and YPG. “Till now, our diplomatic attempts are ongoing to deter this.”

Turkish President Tayyip Erdogan declared on Wednesday that he would launch an operation within days into northeast Syria, where some 2,000 U.S. troops stand alongside the SDF. He said the target was not U.S. soldiers.

The Pentagon warned that any unilateral military action would be “unacceptable”.

U.S. support for the YPG has infuriated NATO ally Ankara, which deems the Kurdish fighters terrorists. Turkey says the YPG is an extension of the outlawed PKK movement that has waged a decades-long insurgency in southeast Turkey.

FIGHT TO THE DEATH

Kobani said Turkey had been mobilizing Syrian fighters allied to it at fronts bordering the SDF region.

In recent years, Turkish forces have already swept into Syria pushing the YPG out of territory west of the Euphrates. But past offensives have stopped at the banks of the river, partly to avoid direct confrontation with U.S. troops.

Kobani, 50, met with top U.S. diplomat for Syria, James Jeffrey, who came to the SDF region after holding talks in Ankara earlier this week.

“(Jeffrey) knows well that Turkish attacks will make the fight against Daesh fail and all the work between us will go to waste,” Kobani said, using the Arabic acronym for Islamic State.

The SDF suspended its battle against Islamic State in eastern Syria in October due to Turkish cross-border shelling of the north. Ground operations resumed when the U.S. military set up observation posts at the border.

At least 5,000 hardline jihadists remain holed up in the desert enclave in eastern Syria, including some elite forces and members of Islamic State’s Shura Council, Kobani said. This includes some 2,000 foreign fighters, mostly Arabs and Europeans along with their families.

“They have decided to fight till the death. Daesh is still strong,” said Kobani, a former engineering student and activist whose nom de guerre refers to his Kurdish hometown in northern Syria.

Kobani said it was possible that Islamic State leader Abu Bakr al-Baghdadi was in eastern Syria, but the SDF could not be sure because he often disappears.

He said veteran Kurdish YPG fighters were running the offensive, leading thousands of more recently recruited local fighters from the mostly Arab eastern province of Deir al-Zor.

“If there is a Turkish attack, the YPG forces will be forced to come protect the borders, to defend their families,” he said. Without them, “the battle against Daesh is not possible.”