Mazloum Kobani told Reuters, in a rare interview, 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 commander-in-chief 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 US troops stand alongside the SDF. He said the target was not US soldiers.

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

Reporter’s code: 50101