Trade Minister Andrew Robb says he believes agreement on the Trans-Pacific Partnership could be just weeks away.

TPP negotiators are aiming to create a trade bloc around the Pacific rim, including Australia, the US, Japan and Canada.

Progress has been slow, but Mr Robb believes a breakthrough is imminent, and a deal could be struck within weeks.

"Mid-February to mid-March: that'll be, I think, the timeframe," he said.

"We might have to come back again to conclude some things, but that's the intent.

"The final issues, as always, are the most difficult. But everyone seems to be in a mood to find some common ground so that we can get this major, major agreement off the ground."

Any TPP agreement would need to be ratified by each member country before it could come into effect, but that could be difficult.

The US Congress has been keen to protect its domestic agricultural sector in past trade deals, while Japan's historic trade agreement with Australia still kept tariffs in place for its important domestic industries like rice and sugar.

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In Australia, concerns have been raised about the inclusion of an investor-state dispute settlement (ISDS) clause, which would allow corporations to challenge laws passed by the Australian parliament. Plain cigarette packaging is a commonly cited example.

But Mr Robb says he's "quite confident, to be honest" that an agreement, if struck, will be ratified by the member states, including the US.

"The Congress is dominated by Republicans now, and in fact the Republicans are more likely to vote for this sort of agreement," he said.

"The chief US trade negotiator Mike Froman, I know from personal contact with the congressmen over there, he's been keeping them abreast the whole way through. Again, there's always uncertainties, but I do feel there's every prospect that the Congress will pass it.

"It's got to get through every country's parliamentary procedure, including our own.

"I'm not taking any of that for granted, but I think if we do a deal that is as fair and as attractive as the other three [free trade agreements with China, Korea and Japan] were last year, then we should be able to get it through our parliamentary process, and get bipartisan support as we have with the others."