The United States has warned Turkey against launching a new military operation in northern Syria and said that the uneasy NATO ally would be putting US troops at risk.

On Monday, the Turkish President Recep Tayyip Erdogan said that Turkey would soon launch a new military operation into northern Syria to create a 30-kilometre (19-mile) “security zone” along the border.

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Speaking to reporters, state department spokesman Ned Price said, “We are deeply concerned about reports and discussions of potential increased military activity in northern Syria and, in particular, its impact on the civilian population.”

“We condemn any escalation. We support maintenance of the current cease-fire lines,” he said.

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At the United Nations, spokesman Stephane Dujarric said that the priority for war-battered Syria should be a political solution and humanitarian assistance.

“We stand for the territorial integrity of Syria, and what Syria needs is not more military operations from any quarter,” Dujarric told reporters.

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Since 2016, Turkey has launched three offensives into Syria aimed at crushing Syrian Kurdish fighters who assisted the US-led campaign against the Islamic State group, also known as ISIS.

The so-called People’s Protection Units (YPG) are considered “terrorists” by Turkey, which sees them as part of the banned PKK separatist movement at home.

Turkey ordered the last incursion in October 2019 when then US president Donald Trump, following talks with Erdogan, said that US troops had accomplished their mission in Syria and would withdraw.

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Amid a backlash even from some of Trump’s allies, then US vice president Mike Pence flew to Turkey and reached an agreement with Erdogan that called for a pause in fighting.

“We expect Turkey to live up to the October 2019 joint statement, including to halt offensive operations in northeast Syria,” Price said.

“We recognize Turkey’s legitimate security concerns on Turkey’s southern border. But any new offensive would further undermine regional stability and put at risk US forces in the coalition’s campaign against ISIS,” Price said.

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After Trump’s abrupt pullout decision in 2019, the YPG sought protection from Syrian President Bashar al-Assad and Russia, the regime’s main supporter, which saw a prime opportunity to replace the United States as the key player.

Russia and Turkey then negotiated a ceasefire which was mostly held.

Trump soon reversed course on the withdrawal and has some 900 US troops still officially in Syria as part of the fight against the Islamic State movement.

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Earlier this month, Turkey’s president had reiterated his objection to Finland and Sweden joining NATO, only hours after they announced their intention to do so.

Recep Tayyip Erdogan said the two Nordic countries did not need to send delegates to persuade Turkey, a crucial NATO member, of their candidacy.

He is enraged by their willingness to house Kurdish extremists.

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Sweden has already stated that Europe was living in a frightening new reality, referring to Russia’s invasion of Ukraine.

Turkey has criticised Russia’s invasion, helped arm Ukraine – which is not in NATO – and tried to facilitate talks between the sides but opposes sanctions on Moscow. It wants NATO “to address the concerns of all members, not just some.