PM's frank meeting with Saudi crown prince

Malcolm Turnbull has had a frank discussion with Saudi Arabia's deputy prime minister about how to fight Islamic State and its propaganda machine.

The prime minister and Crown Prince Mohammed bin Naif discussed IS during a bilateral meeting on the sidelines of the United Nation's general assembly in New York on Tuesday.

Mr Turnbull raised the need to challenge extremist propaganda, especially on social media.

The discussion also focused on the difficulties of creating a clear path towards a political settlement in Syria.

The prime minister also reiterated Australia's commitment to negotiating a free trade agreement with the Gulf Cooperation Council.

Earlier, Mr Turnbull told reporters he would be discussing a range of issues with the crown prince.

"In recent times I've had very detailed, frank discussions with President el-Sisi of Egypt, President Erdogan of Turkey," he added.