Australia is "open" to a United States request for more troops to be sent to Afghanistan, with Prime Minister Malcolm Turnbull confirming the Government is considering providing additional resources to the war-torn country.

Key points: The US has asked Australia to consider providing additional troops to Afghanistan

The US has asked Australia to consider providing additional troops to Afghanistan PM says the Government is "open to that", Opposition Leader leaves door open to supporting it

PM says the Government is "open to that", Opposition Leader leaves door open to supporting it Australian troops mostly work in a training and support role with local Afghan forces

The request for more help came during a visit to Afghanistan last month, where Mr Turnbull met with US Defence Secretary James Mattis in the capital Kabul.

"We have been asked to consider additional resources, and we are actively considering that. We're open to that," Mr Turnbull told reporters in Sydney.

But the Prime Minister said Australia must first also examine its existing Defence commitments in the region and other parts of the world.

Australian troops in Afghanistan mostly work in a training and support role aimed at strengthening the Afghan forces' ability to protect their own country.

"It is very important that we, and our other allies in the effort in Afghanistan, continue to work together to build up the capacity of Afghanistan's own security forces so that they can keep that country secure from the threat of terrorism," Mr Turnbull said.

Opposition Leader Bill Shorten also left the door open to supporting a move to send more troops.

"When it comes to our national security, we've got a good track record of working with both Tony Abbott and currently Malcolm Turnbull," Mr Shorten said.

"These matters are very important.

"I expect the Government will brief us at the appropriate time."

Australian troops are expected to remain in Afghanistan, which is battling a resurgent Taliban along with militants from the Islamic State group, for at least two more years.

That will take Australia's commitment in the country to 18 years.