Pentagon chief warns US will 'prevent unacceptable offensive' by Turkey against Syrian Kurds

The US said on Tuesday that it would prevent an "unacceptable" offensive by Turkey to remove a Kurdish militia from northern Syria.

Turkey has long warned it would launch an operation east of the Euphrates river, ostensibly to create a "safe zone" guarding its borders from the Syrian Kurdish forces which Ankara regards as a terrorist group.

Defence Secretary Mark Esper on Tuesday said that such a unilateral attack on the US-backed YPG , forewarned again on Sunday by Turkish President Recep Tayyip Erdogan, would be "unacceptable".

Speaking to reporters during a trip through Asia, the Pentagon chief said US officials were trying to come to an "arrangement" that would address Turkish concerns but prevent a unilateral incursion into the Kurdish-administrated territory.

"Clearly we believe any unilateral action by them would be unacceptable," Esper said.

"And so what we are trying to do now is work out with them an arrangement to address their concerns and I am hopeful we will get there... what we are trying to do is prevent unilateral incursions."

Last-ditch negotiations over Ankara's hoped-for "safe zone" between US defence officials and their Turkish counterparts are currently underway.

Washington has backed the YPG as the main fighting force against the Islamic State group in Syria.

Read more: Elusive US-Turkey deal over Syrian safe zone complicated by S-400 crisis

Ankara however points to the militia's links to the Kurdistan Workers' Party (PKK), a Kurdish insurgent group engaged in an on-off civil war with the Turkish state since the 1980s.

The PKK is designated as a terrorist group by Turkey, NATO, the United States and other nations.

Washington earlier this year proposed setting up a 30-kilometre (18-mile) "safe zone" on the Syrian side of the border.

The Turks insist that such a buffer zone should be under Ankara's administration, but the Kurds have rejected any Turkish involvement and instead proposed a 5-kilometre (3 mile) zone.

Ankara renewed threats to launch an offensive against the YPG if talks fail to reach a "satisfactory" conclusion.

"We can only be patient for so long. That patience will come to an end," Erdogan said on Sunday.

Turkey has twice carried out unilateral offensives into northern Syria against the Islamic State group and YPG, in 2016 and 2018 respectively.

"For the US, as things stand, succumbing to Turkish demands over the safe zone would be tantamount to giving Ankara the keys to northern Syria. Especially so when considering the swaths of territory that Turkey already controls around the towns of Afrin and al-Bab," analyst Bashdar Ismaeel wrote for The New Arab on Monday.

Turkey demands the border zone be rid of Kurdish forces and patrolled by Turkish troops and their Syrian rebel allies.

"The only logical solution is a US-EU force to patrol and control the cease-fire line in the buffer zone, but this would require a sizable and long-term force that neither Washington nor their European allies seem willing to commit," Ismaeel wrote.

"If an agreement over the safe zone continues to falter, the fate of any Turkish military incursion will hinge on the appetite of the US forces to protect the Kurds."