Washington: Up to 1,000 additional US troops could deploy to northern Syria under provisional plans drawn up by the Pentagon, a US defense official told AFP on Wednesday.

The plans, which still need to be approved by President Donald Trump and Defense Secretary Jim Mattis, would mark a significant uptick in US boots on the ground in Syria as part of the fight against the Islamic State group.

Currently, the troop level is capped at 500 in Syria, but that number has become increasingly meaningless as commanders flow extra "temporary" forces in as needed -- such as last week's deployment of a Marine artillery battery near Raqa.

The actual number of American troops in the war-torn country is likely now between 800 and 900, and a US defense official said the new plans would allow for up to 1,000 more.

"That's one of the proposals that's on the table for discussion," the official said, speaking on condition of anonymity.

The possible deployment was first reported by the Washington Post, which said the extra forces would come from the 24th Marine Expeditionary Unit and the US Army's 82nd Airborne Division.

The official said the troops would not be directly in combat, but rather in support roles for any additional capabilities the military requires in northern Syria, where a US-led coalition is training and backing a local Kurdish-Arab alliance to fight the Islamic State group.

Such missions could include additional artillery batteries and the use of rocket launchers known as HIMARS that might be used to provide round-the-clock bombardment in the battle to recapture Raqa from IS.

Former president Barack Obama was loath to deploy combat troops into Syria and Iraq to fight IS, arguing the battle could only be meaningfully won by local forces.

Trump has said he wants to quicken the defeat of IS and told the Pentagon to come up with a range of plans that could accomplish that goal.