Sept. 8 (UPI) -- The Pentagon sent more than 100 U.S. Marines to reinforce a coalition outpost in southern Syria after a threatened attack from Russia, U.S. officials said.
Russia threatened to attack militants, who they refer to as terrorists, near outpost base At Tanf, a town close to Syria's borders with Iraq and Jordan, in messages sent to the United States in recent days.
The U.S. Operation Inherent Resolve coalition uses the At Tanf Garrison to train Syrian fighters who are confronting Islamic State militants.
"The United States does not seek to fight the Russians, the government of Syria or any groups that may be providing support to Syria in the Syrian civil war," said Lt. Col. Earl Brown, a spokesman for U.S. Central Command. "However, the United States will not hesitate to use necessary and proportionate force to defend U.S., coalition or partner forces."
U.S. Central Command said the forces sent to Syria would conduct exercises using live ammunition near At Tanf, around which the U.S. has declared about a 35-mile de-confliction zone.
"Our forces will demonstrate the capability to deploy rapidly, assault a target with integrated air and ground forces, and conduct a rapid exfiltration anywhere in the OIR combined joint operations area," said Navy Capt. Bill Urban, a spokesman for U.S. Central Command. "Exercises like this bolster our defeat-ISIS capabilities and ensure we are ready to respond to any threat to our forces."
Russia has repeatedly alleged that the United States is harboring ISIS inside the zone, but the United States has vehemently denied this and suggested that Russia merely wants an excuse to attack the area.
"Coalition partners are in the At Tanf deconfliction zone for the fight to destroy ISIS," Brown said. "Any claim that the U.S. is harboring or assisting ISIS is grossly inaccurate."
At Tanf is a key U.S. stronghold near the border of Syria, Jordan and Iraq, used to root out militant troops in the area, as U.S.-Russian tensions increase.
Syrian forces are closing in on the Idlib province in northwest Syria, the last stronghold for rebels who have failed over the past seven years to oust President Bashar al-Assad.
James Jeffrey, U.S. special representative for Syria, warned Thursday, "there's lots of evidence that chemical weapons are being prepared." Jeffrey added that the attack would be a "reckless escalation."
Amnesty International said that many residents of Idlib are already refugees from elsewhere in Syria and cannot withstand another offensive.
The Trump administration warned government officials in Russia and Syria against a planned Idlib offensive in a tweet Monday.
"President Bashar al-Assad of Syria must not recklessly attack Idlib Province," Trump said. "The Russians and Iranians would be making a grave humanitarian mistake to take part in this potential human tragedy. Hundreds of thousands of people could be killed. Don't let that happen!"
Despite this warning, Syrian government warplanes attacked the province Tuesday.
The attack was assisted by the Russian military, which called the area a "cradle of terrorism," the BBC reported.