It has made it more difficult for US negotiators to cut last-minute deals needed to finalise the agreement this week, he says, meaning the President's hopes of finalising the deal in his final term may be fading fast.

The world's biggest multilateral trade agreement, called the Trans-Pacific Partnership, is being negotiated by global trade ministers over the next two days in Atlanta, Georgia in the United States.

The massive deal will cover 40 per cent of the world's economy and bind 12 economies in the Pacific region more closely - Australia, New Zealand, Canada, the United States, Mexico, Peru, Chile, Malaysia, Singapore, Vietnam, Brunei and Japan.

It will also cement US labour and environmental practices within the region's trade relationships, creating a blueprint for future trade agreements with countries such as China.

Trade officials believe the negotiations have been nearing completion - after five long years of talks - with only a few key sticking-points preventing the agreement from being concluded this week.

But Mr Robb has told Fairfax Media that the attempt by US President Barack Obama to get the deal done more quickly earlier this year has made it harder for US negotiators to move past those sticking points.

President Obama has openly been pushing for the trade deal to be completed quickly because he would like it to form part of his economic legacy, but he needs to get it finalised and submitted to Congress as soon as possible so it has time to pass before he leaves office next year.

In June this year he won the controversial power to send an eventual finalised trade agreement to Congress for approval without Congress having the power to make amendments to the bill, significantly reducing the time it will take for the bill to pass once it gets to Congress.

But Mr Robb says President Obama had to make numerous promises to senators to get that power, and a consequence of that is that US negotiators now say they can't cede any more ground on key sticking points in the final crucial stage of the negotiations.

"The [fast track authority] has a lot to answer for in all of this, because a lot of the Congressmen said 'sure, you'll get our vote, as long as you do X, Y and Z', which usually meant not opening up as much as the administration would want to," Mr Robb said.

"It's tied their hands. They say 'Well, we can't move because of Congress, and I say well, you know, you're not on your own, we all have politics to deal with [back home]."

"Clearly a lot of commitments were made in order to get the votes to get the [fast track authority] through, and it can be somewhat frustrating."

Mr Robb said he was still waiting to see what deal the Americans were going to offer Australia on dairy products.

"We've put stuff forward to the Americans on biologics, and we're waiting for them to come back with a response. And we're waiting on the Americans [to come to us with something on] dairy, [but] they claim they're waiting on others," he said.

"We're in that stage which can be quite frustrating."

Earlier in the morning, a dozen protesters were asked to leave the Westin Hotel in downtown Atlanta, the site of the negotiations, after they walked inside and began yelling in unison "Stop the TPP! No corporate greed!"

Cancer patient Zahara Heckscher, in a T-shirt reading "I HAVE CANCER. I CAN'T WAIT 8 YEARS", was arrested for refusing to leave the hotel.

Ms Heckscher was demanding that trade officials show her the secret text of the agreement so she could see if it included a 'death sentence clause' - the text of the US proposal to extend de facto monopolies on biological medicines from 5 to 8 years.

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