The Pentagon has urged Turkey to stand down on its plan to invade Syria as the operation could endanger U.S. troops in the country. 

U.S. Defense Secretary Lloyd Austin offered his condolences to his counterpart Turkish Minister of National Defense Hulusi Akar for the loss of life in the Istanbul bombing that occurred last month and prompted military action in Syria. 

But Austin stressed that the airstrikes – and the impending ground invasion of Syria – directly threatens the safety of U.S. personnel working in Syria. 

"Secretary Austin called for de-escalation, and shared the Department’s strong opposition to a new Turkish military operation in Syria," according to a readout of the call between Austin and Akar. 

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Turkey launched a series of airstrikes in northern Syria following the bombing on Nov. 13 that killed six people and injured at least 80 other people. 

Defense Secretary Lloyd Austin

U.S. Secretary of Defense Lloyd Austin speaks during a press briefing after a virtual Ukraine Defense Contact Group meeting at the Pentagon on Nov. 16, 2022, in Arlington, Virginia.  (Alex Wong/Getty Images)

Turkish authorities arrested an Arab Syrian woman whom they linked with Kurdish militias, but the militias denied any involvement. 

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Turkish President Tayyip Recep Erdogan authorized a military response in Syria, called "Operation Sword-Claw," which aimed to take out the People’s Defense Units (YPG) and the Kurdistan’s Worker’s Party (PKK). 

Erdogan NATO

Turkey's President Recep Tayyip Erdogan speaks during a news conference, in Ankara, Turkey, on May 14.  (AP Photo/Burhan Ozbilici)

A Kurdish general told Fox News last week that NATO ally Turkey is planning to carry out a massive ground invasion of Syria in an effort to target the same Kurdish groups that partnered with the U.S. military in its campaign against ISIS.

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U.S. military officials have also raised concerns that the operation could end up providing an opportunity for some 10,000 ISIS detainees to escape confinement. 

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Women walk in the al-Hol camp that houses some 60,000 refugees, including families and supporters of the Islamic State group, many of them foreign nationals, in Hasakeh province, Syria, May 1, 2021.  (AP Photo/Baderkhan Ahmad, File)

Brigadier Gen. Patrick Ryder, the Pentagon’s press secretary, said Wednesday, "Recent air strikes in Syria directly threatened the safety of U.S. personnel who are working in Syria with local partners to defeat ISIS and maintain custody of more than 10,000 ISIS detainees."

Ryder noted that an "Immediate de-escalation is necessary to maintain focus on the defeat-ISIS mission and ensure the safety and security of personnel on the ground committed to the defeat-ISIS mission."

One military official said that Syria presents ideal conditions for ISIS to continue growing its ranks and regaining its former operating capacity: CENTCOM chief Gen. Erik Kurilla visited the al-Hol refugee camp in Syria and said ISIS has looked to exploit the conditions in the camp as a means of gaining new recruits to its cause. 

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"The SDF mission to clear ISIS from the camp continues: This is a critical, wide-ranging operation which will make the camp safer for all residents," Kurilla said following his visit. "We’ve already seen ISIS members holding women and girls enslaved in chains inside the camp, torturing camp residents, and seeking to spread their vile ideology."

Fox News’ Benjamin Weinthal contributed to this report.