The US military is indirectly supporting Syrian leader Bashar al-Assad in an effort to help him defeat jihadist groups, according to a report by a veteran but controversial US journalist.

The report by Seymour Hersh, claims that despite its avowed public policy of opposing the Syrian leader, the US is providing intelligence through third party nations, including Russia, Germany and Israel. It did so on the understanding that that the Syrian leader would use it to confront Isis and Jabhat al-Nusra, another extremist group.

Mr Hersh’s report - published in the London Review of Books - claims that the Joints Chiefs of Staffs (JCS) move was rooted in several concerns, including the US arming of unvetted Syrian rebels with jihadist ties, a belief the administration was overly focused on confronting Mr Assad’s ally in Moscow.

Mr Hersh has made a number of claims about US foreign policy (YouTube)

There was also anger that the White House was unwilling to challenge Turkey and Saudi Arabia over their support of extremist groups in Syria.

The report claims there was a clear gap between the thinking of the military leader and the political leadership of President Barack Obama and his administration.

“We weren’t intent on deviating from Obama’s stated policies,” a former senior adviser to the JCS told Mr Hersh.

“But sharing our assessments via the military-to-military relationships with other countries could prove productive. It was clear that Assad needed better tactical intelligence and operational advice.

“The JCS concluded that if those needs were met, the overall fight against Islamist terrorism would be enhanced. Obama didn’t know, but Obama doesn’t know what the JCS does in every circumstance and that’s true of all presidents.”

There has been no public comment on Mr Hersh’s claims, which would amount to a case of US military chiefs undermining the civilians leadership of President Barack Obama and his administration. The Pentagon did not immediately respond to inquiries.

It is not the first time Mr Hersh has made controversial claims over aspects, or incidents, of the US’s foreign policy.