Tony Abbott says Australia could step up its efforts in Iraq, as Foreign Minister Julie Bishop expressed deep concern about foreign fighters becoming involved in a wider range of terrorist groups.
Ms Bishop is in Washington where she received briefings from US intelligence and defence chiefs, as well as meeting Vice President Joe Biden and Secretary of State John Kerry.
US President Barack Obama said in his State of the Union speech on Wednesday that the world needed to keep up a "relentless" effort to hunt down terrorists and dismantle their networks.
Mr Obama said the fight against Islamic State would take time and "require focus" but it would succeed.
Prime Minister Abbott said Australian military forces were making a significant contribution, but he acknowledged the fight was ongoing.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"I certainly don't rule out doing more, but I think it needs to be recognised that we are doing a lot as things stand," Mr Abbott told Fairfax radio.
Australia has 600 personnel conducting air strikes and supporting Iraqi security forces, the second largest contribution to the international coalition behind the US.
Islamic State has recruited at least 180 Australians either directly fighting in Iraq and Syria or supporting the extremist organisation from home.
Ms Bishop said after her meetings she was "deeply troubled" about the threat posed by foreign fighters, and not just those involved in IS, also known as ISIL.
"I'm even more troubled by the phenomena of foreign fighters because of the way they are organised, because of the way they are metastasising," she said.
"We are seeing Al Qaeda, Al Nusra, Al Qaeda in the Arabian Peninsula claiming to have taken part in attacks, so it's not just ISIL ... there are many other terrorist organisations upon whom our focus is warranted."
Ms Bishop didn't expect the US would be seeking more Australian support in Iraq.
The White House said in a statement the vice president had thanked Ms Bishop for Australia's "significant contributions" to countering the threat posed by ISIL and helping Iraq strengthen its security forces.
Ms Bishop said in a speech to the Brookings Institute in Washington that Australia and its allies, such as the US and Britain, must be prepared "to lead and to adapt".
"Terrorism is now more global, more dangerous, more diversified than ever before," Ms Bishop said.
This made it all the more important for Australia and the US to improve the stability and governance of places such as Afghanistan and Iraq.
"We're fighting in the Middle East today for this very reason: to end the opportunities that lawlessness and weak sovereignty provide for terrorist and criminal networks to grow."
