THE Turnbull government has rejected a request from the United States for more military help in the Middle East campaign against Islamic State.

US Defence Secretary Ash Carter in December asked coalition partners fighting the extremist group in Iraq and Syria for a greater commitment following the Paris attacks.

But Defence Minister Marise Payne remained firm on Australia’s existing level of assistance.

“Australia has considered the request ... in light of the substantial contributions we are already making to train Iraqi security forces and to the air campaign,” a spokesman for the minister told AAP in a statement today.

“The government has advised secretary Carter that our existing contributions will continue.”

US Ambassador to Australia John Berry played down the response, saying it elicited “absolutely no disappointment”.

“There is great gratitude from Washington for the role Australia has played,” he told the Seven Network.

The minister said Australia’s contribution could be reviewed in consultation with coalition partners.

Australia would increase the number of defence personnel in coalition headquarters from 20 to 30, as well as offer more airlift support on humanitarian efforts.

The government is also considering providing more humanitarian support for Syria and Iraq in the coming months.

Prime Minister Malcolm Turnbull is due to meet US President Barack Obama in Washington next week.