By Agencies

CENTCOM says US is not controlling "any airfield in Syria", despite images appearing to show air strip expansion works.

The US has denied taking control of a Syrian air strip in response to an opposition group's claim that American troops are supporting Kurdish fighters in northern Syria with such a takeover.

On Friday, a spokesman of the United States Central Command (CENTCOM) said that the military "denied that US forces have taken control of any airfield in Syria".

However, also on Friday, the website of Texas-based security analyst Stratfor said that satellite "imagery supports claims of US military activity in Syria", as it posted graphics appearing to show an expansion of the airfield's runway.

On Wednesday, the Syrian Democratic Forces (SDF) said the US had taken control of the Rmeilan air strip in Syria's northern province of Hasakah to support Kurdish fighters against the Islamic State of Iraq and the Levant (ISIL) group.

The air strip near the city of Rmeilan was previously controlled by the US-backed Kurdish People's Protection Units (YPG). The formerly disused runway is close to Syria's borders with Iraq and Turkey.

"The new and improved infrastructure could help the Syrian Democratic Forces conduct offensive operations against the Islamic State. The United States has already carried out two weapons airdrops to the rebel Syrian Arab Coalition, a faction of the Syrian Democratic Forces," Stratfor said on its website.

Taj Kordsh, a media activist from the SDF said on Tuesday: "Under a deal with the YPG, the US was given control of the airport. The purpose of this deal is to back up the SDF, by providing weapons and an airbase for US warplanes.

"This airport was previously controlled by the YPG for over two years now. This strategic airport is close to several oil bases - one of the biggest in this area.

"Rmeilan airport was previously used for agricultural purposes by the Syrian government."

Previous reports published by the Syrian Local Coordination Committees say that the US has been preparing and expanding the Rmeilan airstrip for a while now.

READ MORE: Kurdish-Arab coalition in Syria forms political wing

The US has previously supplied the SDF with weapons. It also backs the group with its air strikes in their fight against (ISIL) in northern Syria.

The SDF was founded in Syria's mainly Kurdish northeastern region in October 2015, and is made up of at least 15 armed factions - mostly fighters from the YPG and the Free Syrian Army.

The fighters include Christians, Arabs and about 500 foreign fighters, Kordsh said, adding that some groups in Aleppo and Idlib pledged allegiance to the SDF last month. 

The UK-based Syrian Observatory for Human Rights monitor also reported on Tuesday that the US had taken control of the airbase. 

Sourcing activists, the Observatory said the airfield is still being prepared for use by the US.