US President Barack Obama has authorized the first sustained deployment of special forces to Syria, relenting on a long-standing refusal to put US boots on the ground.

US President Barack Obama has authorized the first sustained deployment of special forces to Syria, the White House said Friday, relenting on a long-standing refusal to put US boots on the ground.

Spokesman Josh Earnest said that Obama okayed a deployment of "fewer than 50" special operations forces in the north of the country in a bid to strengthen armed groups fighting what he called 'Islamic State of Iraq and the Levant' (ISIL) takfiri group.

The White House denied the move was a reversal of Obama's pledge not to put combat troops in Syria, saying Americans would not be "leading the charge up the hill" and insisting it was not evidence of "mission creep."

"Our strategy in Syria hasn't changed," said Earnest.

Instead, officials indicated the mission would echo some US operations in Iraq, where military personnel coordinate local ground forces, channel weapons supplies and direct air support.

The White House announced Friday the deployment of A-10 ground-attack planes and F-15 tactical fighter jets to the Incirlik base in southern Turkey and increased assistance to Lebanon and Jordan as part of the ramped up effort.

Obama recently scrapped a $600 million mission to train what he called "moderate Syrian opposition fighters" fighting ISIL and al-Nusra Front takfiris.