HANOI (Reuters) - Vietnam will not include ratification of the Trans-Pacific Partnership (TPP) on its agenda for its next Parliament session, an official said on Friday (Sept 16), adding to uncertainty over the future of United States President Barack Obama's signature trade deal.

As arguably the biggest beneficiary of the deal covering 40 per cent of the global economy, Vietnam was expected to be among the first to ratify the TPP, the prospect of which helped spur record foreign investment last year in its booming manufacturing sector.

"TPP will not be on the assembly's agenda because the government's proposal is not completed," a Parliament source familiar with the matter told Reuters. He did not elaborate.

Vietnamese ratification was widely considered a formality, having already been approved in January by the top brass of the ruling Communist Party.

The National Assembly is 96 per cent comprised of party members and domestic opposition to the TPP is unheard of. Its next session begins on Oct 20.

The delay means that at the earliest, ratification by Vietnam would be several months after November's US presidential election, the run-up to which has seen its trade policy come under heavy domestic scrutiny.

Negotiations were completed last year for the TPP, dubbed a "mega-regional accord", to create a trading zone of 12 members with a combined US$27 trillion gross domestic product (GDP).

It seeks to raise standards and challenge China's economic influence and debate in the US has caused jitters among some of its members, which include Japan, Malaysia, Singapore, Brunei, Peru, Chile, Australia, New Zealand, Canada and Mexico.

Mr Obama has expressed confidence of winning congressional approval for TPP before he leaves office, warning that failure to do so would undermine US leadership in the region and allow China to set the rules of regional commerce.

With Vietnam's strengths in electronics, textiles, seafood and commodities, the TPP is seen as a game-changer for its export-dominated economy, and a means of boosting US influence in China's backyard.

Friday's Thanh Nien (Young People) daily newspaper cited Ms Nguyen Thi Kim Ngan, the Parliament chairman, as saying Vietnam's ratification would depend on the Communist Party, the global situation and the outcome of the US election.

The prospects for US legislative approval of the TPP have looked increasingly dim, with both presidential candidates - Democrat Hillary Clinton and Republican Donald Trump - stating their opposition to the pact, in its present form at least.