Prime Minister Tony Abbott said it was "fanciful" that he would unilaterally propose sending a large number of Australian troops to fight Islamic State in Iraq without any international co-operation.

"We do not act unilaterally in the Middle East," he told reporters in Darwin.

Tony Abbott reportedly called for 3500 Australian troops to fight IS in Iraq. Credit:Christopher Pearce

According to the report in The Australian, in a meeting on November 25 last year, Mr Abbott suggested a unilateral invasion of Iraq by about 3500 ground troops to help stop the advance of Islamic State forces through the ravaged country.

But the idea was reportedly shot down by government military advisors, who were stunned the Prime Minister would suggest endangering Australian troops with no NATO or US cover to assist them.