WASHINGTON: Some of the 1,500 new US troops authorised to advise and train Iraqi forces in their fight against Islamic State militants will deploy to the country in the next few weeks without waiting for Congress to fund the mission, the Pentagon said on Thursday.

Rear Admiral John Kirby, the Pentagon press secretary, said leading elements of the US force would begin moving to Iraq in the coming weeks, even if Congress has not yet acted on a $5.6 billion supplemental request to fund the expanded fight against the militants who overran northwestern Iraq earlier this year.

Officials initially indicated they needed to lawmakers to approve the funding before the Pentagon could start the mission, but General Lloyd Austin, the head of US troops in the Middle East, recommended starting the effort using resources already available to him.

“The commander ... can reallocate resources inside his theater as he deems fit. So he is going to .. try to get a jump start on this program,” Kirby told reporters, adding that congressional approval of the $5.6 billion was still needed to carry out the “more robust program.”

Kirby's comments came just days after US officials said some 50 special operations troops had been sent to Ain al-Asad air base in Anbar province in Iraq to establish an operation to advise and train Iraqi troops.

President Barack Obama's administration announced on Nov 7 plans to roughly double the number of US troops in Iraq, adding an additional 1,500 to establish sites to train nine Iraqi military brigades and three Kurdish peshmerga brigades.

Kirby said Austin thought starting the expanded mission sent a message both to Iraqis and other coalition partners.

“It sends an important signal ... about how seriously we're taking this,” Kirby said. “The sooner we get started, the sooner Iraqi units will improve ... and the sooner we'll get coalition contributions to that particular mission.”

Kirby indicated additional US troops would begin deploying to Iraq before the end of the year.

“You're going to start to see initial elements of the 1,500 or so additional start to flow in the next few weeks,” he said. “I think certainly by the end of the calendar year you're going to see a much more robust presence, not just by the United States doing this but by coalition partners as well.” .