Satellite images reveal US airbase in Syria

The Rmeilan airfield, located in northwest Syria near both Turkish and Iraqi borders, is also close to territory controlled by the Islamic State group.

Rumours of a US presence in Rmeilan surfaced earlier this month.

"The images confirm that at least some of those rumours are true," the report said.

The airfield has had its runway nearly double in size, from 700 to 1300m enabling it to accommodate larger aircrafts.

The expansion will provide landing space for US Hercules aircrafts which are the central supply and transport craft in the US military's fleet.

The Kurdish People's Protection Units (YPG), who are now major participants in the Syrian Democratic Forces (SDF) along with Arab fighters, have controlled the area for the last two years.

The US military is providing the SDF with arms and logistical support in their fight against IS militants.

"Expanding the Rmeilan runway could expedite this process by allowing US airplanes to land and drop off supplies instead of continuing to rely on airdrops," said the Strafor report.

US officials confirmed that a small number of special forces soldiers were being deployed on the ground but declined to give details.

The expansion of the Rmeilan airfield follows a phase of notable SDF advances against IS militants.

"Because of the special nature of these forces, it's very important that we do not discuss specifically where they're located," said Colonel Steve Warren, an army spokesman, in Baghdad.

The expansion of the Rmeilan airfield follows a phase of notable SDF advances against IS militants that have brought them closer to the city of Raqqa, the IS 'capital' in northern Syria.

In December 2015, the SDF seized the strategically critical Tishreen Dam from IS in a major operation after removingIS fighters from more than 200 villages in the province of Hasakah.