Ministers from 11 Trans-Pacific Partnership countries are scheduled to gather Sunday in Hanoi, with Japan to push for the massive free trade pact to be put into force as soon as possible without the United States.

Japan, the biggest economy among the 11 nations, is keen to gain agreement on "high-level rules" agreed on under the TPP, even though the United States withdrew in January due to President Donald Trump's preference for bilateral trade deals, government officials said.

Some countries that hoped to boost exports to the United States may be reluctant to implement just the 11-party TPP, arguing that without the world's largest economy the pact would little benefit their economies.