Malcolm Turnbull is optimistic about the defeat of Islamic State on battlefields in Iraq and Syria, following briefings with top US defence and security officials.
But he is warning the threat of lone-wolf attacks in other countries will get worse before they get better.
Fresh from wrapping up his time at the United Nation's general-assembly in New York, the prime minister met with Defense Secretary Ash Carter at the Pentagon on Thursday local time.
He was also briefed by the directors of the National Security Agency, CIA and National Intelligence.
US-led coalition forces are continuing to roll back the terrorists in Iraq, the prime minister said.
"We look forward to further gains over the course of the next six-months or so," he told reporters in Washington.
"There is a very real prospect of completing the defeat of Daesh in the battlefield, ending their so-called caliphate."
Mr Turnbull said he did discuss timing and dates on the war against Daesh, the Arabic word for Islamic State, with Secretary Carter, but refused to discuss them publicly.
"There is real progress being made towards the recapture, the liberation of Mosul and of course Raqqa as well, but these operations will take their own course."
He stressed the importance of a political solution in Iraq, as well as Syria.
But there are other fears back home.
"There is a concern that the lone-actor-terrorist threat in countries like the United States, Australia, the West if you like, will get worse before it gets better," Mr Turnbull said.
Intelligence was key to stopping lone-wolf attacks, he added.
