A man walks past the Hagia Sophia Grand Mosque in Istanbul, Turkey on April 1, 2022, on the eve of the first day of the Muslim holy month of Ramadan. Photo: AFP

The US on Tuesday warned Turkey against launching a new military operation in northern Syria, saying the uneasy NATO ally would be putting US troops at risk.

Turkish President Recep Tayyip Erdogan said Monday that Turkey would soon launch a new military operation into northern Syria to create a 30-kilometer "security zone" along the border.

"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," State Department spokesperson Ned Price told reporters.

At the United Nations, spokesperson 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.

Turkey has launched three offensives into Syria since 2016 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.

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.

Erdogan's talk of an offensive comes as he threatens to block the NATO membership of Finland and Sweden, which have sought to join the Western alliance out of alarm at the Russia-Ukraine crisis.

Erdogan has alleged support for the PKK in the two Nordic states, which are planning high-level talks with Turkey to ease its concerns.

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

Russia and Turkey then negotiated a cease-fire which has 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.

President Joe Biden has shown no eagerness to pull out the troops despite his exit from the 20-year war in Afghanistan in 2021.

AFP