A huge regional trade agreement which would underpin Barack Obama's "pivot" to Asia could be sealed within weeks, says Trade Minister Andrew Robb.

The catch, however, is that a fast-track approval process from the US Congress has failed to materialise, thanks to a wild-card Democratic senator, Elizabeth Warren, as she positions to woo left-leaning voters from Hillary Clinton ahead of the coming presidential race.

The US-led Trans-Pacific Partnership, covering 12 countries and 40 per cent of the world economy, is tipped to entrench an open, rules-based economic system in the Asia Pacific region, according to experts in Washington and Canberra.

Mr Robb and other close observers have told Fairfax that negotiators are poised to strike a ground-breaking deal which would bring huge economic benefits to Australia and mark a major strategic win for the United States, as it wrestles with China for regional leadership.