The US pushed for as much as 12 years. Australian Trade and Investment Minister Andrew Robb successfully held the line at five years in the final deal, prompting Senator Hatch to last month accuse Australia of being "greedy".

Populist conservative presidential candidate Donald Trump has criticised the deal President Obama struck, arguing it does not clamp down on currency manipulating countries and will allow too many cheap imports.

Many Democrats in Congress also oppose the TPP, fearful it will eliminate blue collar working class jobs in favour of cheaper labour at manufacturing hubs in Asia and South America.

Adding to the uncertainty, presidential frontrunner Hillary Clinton has already declared she does not support the TPP in its current form, in an ostensible appeasement of left-wing Democrats.

The mounting opposition on both sides of politics, albeit for different reasons, means President Obama may need to thread the needle on legislating the agreement in the so-called "lame duck" period after next November's presidential and congressional elections.

The two month window before a new President takes office and when congressional members are under less pressure after the poll, could be the best opportunity to gain a majority of votes in the House and Senate.

In a Washington Post interview published on Friday, Senator McConnell signalled that he was undecided on how he would vote on the deal and that a vote should be delayed.

"It certainly shouldn't come before the election. I don't think so, and I have some serious problems with what I think it is," he said.


"But I think the president would be making a big mistake to try to have that voted on during the election. There's significant pushback all over the place."

Matthew Goodman, a former international economic adviser to President Obama, said on the weekend Senator McConnell's statement was "certainly a blow" to the agreement passing Congress by mid 2016.

"I do remain confident that TPP will be passed assuming cooler heads prevail, the only question is when," said Mr Goodman, now an Asia Pacific adviser at Washington think tank the Center for Strategic and International Studies.

Pro-free trade House speaker Paul Ryan and business groups, originally strong backers of the TPP concept, have said they need more time to assess the details.

It is possible Republicans are trying to bargain with the administration, to try and force the US back to the negotiating table with the 11 other countries or to extract concessions on domestic political policies.

Mr Obama has sold the deal at home as a win for American businesses and workers, and a way to stop rival China writing the international economic rules in Asia.