( CNN) Russia and the regime of Syrian President Bashar al-Assad are attempting to seduce US-backed rebels based at the At Tanf garrison in southern Syria to switch sides, US officers tell CNN, in an apparent bid to depose the coalition from a strategic piece of real estate that is seen as crucial to Syria and Iran's long-term interests in the region.

It's only the latest gambit in a months-long tug of war between the US and Assad and his Russian and Iranian backers in the Syrian desert.

One official said the recruitment campaign, which appears to have had very limited, if any, success to date, is also intended to mid-level commanders of the groups being developed and equipped by the US-led alliance at the At Tanf base which sits in near the tri-border area of Syria, Jordan and Iraq.