The US is to send a small number of special forces troops to Syria to advise rebel groups, sources familiar with the matter told Reuters. Twenty or 30 troops will be deployed to rebel groups fighting Islamic State, an official said.

The move marks an escalation of US attempts to strengthen rebel groups in Syria, as a precondition to finding a diplomatic solution to the conflict. The Obama administration is expected to confirm the deployment on Friday, October 30.

A White House spokesman told the Guardian: "We have no intention of changing our broader counter-ISIL mission to train, advise and assist local partners in the fight to degrade and destroy ISIL. And we have no intention of engaging in long-term, large-scale combat operations the likes of which we previously saw in Iraq and Afghanistan.

"At the same time, though, we've also said our ongoing process includes intensifying efforts that are successful."