WASHINGTON - THE United States on Tuesday welcomed Japan's interest in joining talks on a trans-Pacific free trade pact, ahead of a summit of Asia-Pacific economies in Yokohama.

'We're pleased that Japan may be considering taking steps that could help pave the way for its eventual membership in the Trans-Pacific Partnership,' State Department spokesman Philip Crowley said.

'Japan is a valuable and critical part of the trans-Pacific economic system,' Crowley told reporters. 'We are encouraged by Japan's interest in moving toward trade liberalisation.'

Japanese Prime Minister Naoto Kan announced on Saturday that his government would enter negotiations on the trade pact, days before hosting the Asia Pacific Economic Cooperation summit in Yokohama.

Japanese business groups had urged the government to enter talks on the Trans-Pacific Partnership, alarmed as China considers a place at the table and South Korea finalises a sweeping free trade pact with the United States.

But the decision holds political risks for Mr Kan as it may provoke a backlash from Japan's powerful rice farmers, who have long enjoyed protection from cheaper grain imports.

US welcomes Japan interest