The Turnbull government has formally declined a request from the US to increase its military commitment 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 to consider expanding their contribution in the wake of terror attacks in Paris. 
Defence Minister Marise Payne confirmed on Wednesday that Australia had rejected the request and would maintain its current contribution. 
"Australia has considered the request from US Secretary of Defense Ash Carter 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 said. 
"The government has advised Secretary Carter that our existing contributions will continue."
In lieu of further military commitment, Australia would make an "important contribution to command roles" through an increase in the number of ADF personnel in coalition headquarters from 20 to 30, the spokesman said.
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 Government was also considering providing further humanitarian support for Syria and Iraq in the coming months, Minister Payne's spokesman said.
"Our aircraft in the Middle East are available to provide additional airlift support to benefit coalition humanitarian efforts.

 "The Australian Government continues to keep our contribution under ongoing review in consultation with our coalition partners."