A number of federal cabinet ministers were reportedly summoned to a secret meeting in Canberra ahead of a major international development expected out of the US.
Some cabinet members were granted border exemptions to urgently fly to Canberra for Wednesday's meeting, The Sydney Morning Herald and The Age have reported, quoting sources familiar with the development.
Defence Minister Peter Dutton and Foreign Affairs Minister Marise Payne are in Washington for meetings and reportedly joined the meeting via a secure connection.
Opposition Leader Anthony Albanese and three other members of his frontbench were also briefed on the sensitive matter, the newspapers report.
It is expected an announcement, significant to the US and British governments, will be made at 7am Australian time on Thursday.
Prime Minister Scott Morrison will travel to Washington next week for a meeting of the Quad alliance of the US, India Japan and Australia.
The Quad is seen as a counter to China's rising assertiveness in the Asia-Pacific region.
Mr Morrison will have talks with US President Joe Biden, with security, terror threats, Afghanistan and climate change key issues the pair will discuss.
Australian Associated Press