Instead of extolling the virtues of what was expected to be an electoral trump card, Trade Minister Mark Vaile was forced to call a press conference to play down fears the agreement would send the price of medicines skyrocketing.

Vaile also backed away from claims the deal was worth four billion Australian dollars (three billion US dollars) a year to Australia and attacked the opposition Labor Party for criticising it.

'So far the Labor Party have been playing politics with what is a good agreement and one that is in the national interest," Vaille said.

Opposition trade spokesman Stephen Conroy said the deal was a letdown for farmers.

"This is not a free trade agreement and if you're an Australian farmer you've been dudded," he said

The 1,000-page agreement was officially signed three weeks ago and originally scheduled for release Tuesday but it was then delayed as Australian and US negotiators wrangled over its final wording.

The agreement, reached after more than 14 months of negotiations, has come under fire in Australia because it excludes sugar, largely maintains US protection on dairy and beef produce, and gives US pharmaceutical firms the right to appeal measures designed to keep the cost of medicines down.

Vaile said instead the deal was an opportunity to link up with the world's largest economy and denied he had been advised by his negotiating team to walk away from the agreement because Washington had refused to make key concessions.

"We believe on balance at the end of the process it was in the best interests of the nation to go ahead with it," he told Sky News.