Trade ministers of a Pacific Rim trade bloc, including Australia, are meeting in Tokyo, gearing up to roll out and expand the market-opening initiative.

The Pacific Rim free trade agreement, rejected by US President Donald Trump after he took office in 2017, took effect at the end of last year after Australia became the sixth nation to ratify it.

So far, seven of the 11 member countries have done so, and the others are expected to follow through soon.

Known as the Comprehensive and Progressive Trans-Pacific Partnership, it aims to streamline trade and slash tariffs to facilitate more business among member nations with a combined population of nearly 500 million people and GDP of $A18.8 trillion.

Australian Assistant Trade Minister Mark Coulton tweeted from Tokyo that it had been "great to start work on setting the future direction of of the #CPTPP at the first meeting of the CPTPP Commission in Tokyo".

The 11 nations remaining after the US withdrawal amended the pact to enable it to take effect even without Washington's participation.

Vietnam, Canada, Mexico and Singapore also have ratified it. Peru, Chile, Brunei and Malaysia have not yet done so.

The US departure was a huge loss given the size of the American market. But other countries are reportedly interested in joining the trade deal, seen as a first step toward a pan-Pacific free trade zone.

Trump said he was putting "America first" in seeking bilateral deals rather than broader ones like the Trans-Pacific Partnership - the trading group's original name. Members are still hopeful the US might eventually rejoin.

For now, nearly two dozen stipulations sought by the US in the original deal reportedly have been shelved after Washington withdrew, watering down the plan proclaimed by the previous US administration of President Barack Obama as being the "gold standard" for 21st century trade rules.

Separate efforts are underway to forge a free trade arrangement within Asia called the Regional Comprehensive Economic Partnership, which encompasses the 10 members of the Association of Southeast Asian Nations plus Japan, South Korea, Australia, New Zealand, India and China, but not the United States.