AMMAN (Reuters) - A Syrian rebel commander said on Thursday rare military exercises with U.S. marines in southern Syria sent a strong message to Russia and Iran that the Americans and the rebels intend to stay and confront any threats to their presence.

FILE PHOTO:The U.S. flag flutters on a military vehicle in Manbej countryside, Syria May 12, 2018. REUTERS/Aboud Hamam/File Photo

Colonel Muhanad al Talaa, commander of the Pentagon-backed Maghawir al Thawra group, told Reuters the eight days of drills that ended this week at the U.S. military outpost in Tanf were the first such exercises with live-fire air and ground assault, involving hundreds of U.S. troops and rebel fighters.

“These exercises have a big importance and have beefed up the defenses of the area and raised the combat capabilities and morale and that of civilians in the area,” Talaa told Reuters by phone from Tanf, near Syria’s borders with Jordan and Iraq.

A U.S. military spokesman said the exercises were a show of force and that the Pentagon had notified Moscow through “deconfliction” channels to prevent “miscommunication or escalate tension”.

“The exercise was conducted to reinforce our capabilities and ensure we are ready to respond to any threat to our forces within our area of operations’” Colonel Sean Ryan told Reuters in an email response to a question on the exercises.

Russia and the Syrian government have repeatedly called on Washington to pull out its troops from Tanf base, where it has declared a 55 km (35 mile)-radius “deconfliction zone” off-limits to others.

Rebels say hundreds of U.S. marines arrived this month in Tanf to join special operations troops already based in the garrison and participate in the drills, amid heightened U.S.-Russian tensions in Syria and a naval buildup in the Mediterranean.

The “deconfliction zone” has become a safe haven for at least 50,000 civilians who live in the Rukban camp that lies within it. Russia’s defense ministry in August repeated an accusation that Washington has been harboring Islamic State militants within the zone.

“We are staying whether the Russians or Iranians want or not,” the rebel commander added.

The outpost, surrounded by desert, was established during the battles against Islamic State militants who used to control eastern Syria bordering Iraq.

After Islamic State were driven out, U.S.-led coalition warplanes struck Iranian-backed militias on several occasions to prevent them advancing, in what Washington has described as self-defense.

Tanf lies on the strategic Damascus-Baghdad highway, once a major supply route for Iranian weapons into Syria.

This makes the base a bulwark against Iran and part of a larger campaign against Iran’s military expansion in the Middle East.

Control of the area has long been a goal of the Syrian government and its Russian and Iranian allies.

Rebels say the U.S. military’s new policy to bolster Tanf’s capabilities is a big shift.

“The American position has changed completely toward the Iranians. Before it was just putting a line to the Iranians not to approach the areas,” Talaa added.

Tehran’s failure to end its military presence in Syria could provoke a U.S. military response, Talaa added.

“If Tehran does not respond to the demands of the Americans there is a big likelihood they will be hit. It’s inevitable the Iranians leave Syria. This should happen quickly and in a decisive way,” he added.