Australian Prime Minister John Howard has dismissed suggestions that a security declaration with Japan could strain ties with China.
Mr Howard said the deal would bring the two countries closer
Mr Howard is set to sign the ground-breaking deal during a four-day visit to Japan which begins on Sunday.
The agreement is thought to include co-operation on terrorism, peacekeeping and disaster relief.
Australia has been looking to exert more influence in Asia, in terms of business as well as regional security.
Full details of the pact have not been revealed but it is expected to include plans for greater co-operation in dealing with North Korea's nuclear ambitions.
Mr Howard told Japanese journalists in Sydney that the deal "will mean that Australia's security relationship with Japan will be closer than with any other country, with the exception of the United States", Jiji Press news agency reported.
But he said ties with China would not be affected.
"We have a good relationship with China and I don't believe for a moment that this declaration is going to damage our relationship with China," Jiji quoted him as saying.
Free trade deal
Mr Howard has been driven by two principal concerns, the BBC's Phil Mercer reports from Sydney. Firstly his government wants to strengthen counter-terrorism measures with its regional neighbours.
Then there are powerful business considerations. Trade with Asia is the life blood of the Australian economy and a defence pact with Japan is likely to be followed by discussions on a free trade deal.
Analysts believe the defence treaty is further evidence that Japanese Prime Minister Shinzo Abe is keen to pursue closer alliances with countries in the region including Australia and India.
This will be Japan's second bilateral security deal - its other one is the Japan-US Security Treaty which dates from 1960.