The likelihood of US involvement will draw in other nations that have been interested in joining the pact, Mr Yeo told The Straits Times.

His remarks followed US Trade Representative Susan Schwab's announcement of Washington's intention to negotiate its entry in the Trans-Pacific Strategic Economic Partnership Agreement (TPSEPA). The pact is currently confined to Singapore, New Zealand, Chile and Brunei.

Ms Schwab said the accord, when reached, would further America's commercial ties with Asia.

'We are particularly interested in this high-standard agreement potentially serving as a vehicle for advancing trade and investment liberalization and integration across the trans- Pacific region,' she remarked, adding that the accord could form the core of a future broader agreement among Pacific nations.

The US Trade Representative said the negotiations should begin early next year, when a new administration is in place. The first round of talks is to be held in Singapore.

Analysts believe Washington's entry could add more than US$1 billion (S$1.41 billion) a year to Washington's balance sheets, and invigorate the trans-Pacific effort.

Under the agreement, tariffs on all trade products are eliminated within 12 years, with tariffs on 90 per cent of trade in goods among the parties eliminated immediately.

Mr Yeo said that the TPSEPA will be open to any countries that are willing to uphold the agreed-upon standards.

'I know Vietnam is studying it very closely but they are aware that their economy is at a lower level and they would need certain phasing in accomodations,' he said, adding that he was 'hopeful other countries will also come around.'

Australia and Peru have shown interest in signing the accord.

Officials said, just as important is the impact Washington's participation could have on efforts to strengthen the trade agreements already underway between the 21 members of Apec.

The Pacific bloc includes most Southeast Asian states as well China, Russia, Japan, Canada, Australia and the United States.

The group has a stated goal of trade liberalisation, eliminating tariffs on 90 percent of trade immediately, and cutting out all tariffs among members within 12 years. But progress has been slow and the targets are not binding.

APEC member countries account for nearly 60 per cent of global GDP and roughly 50 per cent of all international trade.

'For us, this is a momentus day,' said New Zealand Trade Minister Phil Goff.

'The United States for us is the largest and most critical market,' he said, with trade between the two countries hitting $8 billion.

Chilean Foreign Affairs Minister Alejandro Foxley told reporters that expanding the Trans Pacific Pact to include the United States could reinvigorate stalled global trade talks, known as the World Trade Organisation's Doha Round.

The benefits to the United States of joining are clear: the agreement will facilitate trade and investment between the partners, and promote intellectual property rights, as well as standards for transparency, labor and environment.

Nonetheless, US participation will have to approved by Congress, a potentially lengthy process subject to political roadblocks.

With additional information from Bloomberg