CANBERRA -- Australia's opposition leader is under increasing pressure to support Australia's landmark free trade agreement (FTA) with China.

Bill Shorten faces new pressure to sign off on the deal now that state Labor leaders have said the agreement was "good news" for Australia.

Federal Labor has been hesitant to throw support behind the deal out of fear that it puts Australian jobs at risk, but state Labor leaders such as Victoria's Daniel Andrews and South Australia's Jay Weatherill have already given it the thumbs up.

Adding to the pressure, National Farmer's Federation chief executive Simon Talbot told News Corp that if Australia - or the Labor Party - asked for amendments to the FTA, which is already tipped in "Australia's favor" according to China's Commerce Minister Gao Hucheng, then China would "no doubt" sign a deal elsewhere.

"It was a very clear statement from Minister Gao, they believe they've given Australia the best possible trade agreement, and there's the perception the balance is in Australia's favor," Talbot said on Wednesday.

"I have no doubt that if we blink and baulk at this, they will go elsewhere and that will be South America."

Federal Trade Minister Andrew Robb said the state Labor leaders had made a good decision in supporting the FTA, instead saying federal Opposition Leader Bill Shorten was "out of touch".

"Sadly, Bill Shorten, who's led by the nose by the (trade unions), is still way out of touch on this issue," he said on Wednesday.

Meanwhile former Australian ambassador to China, Geoff Raby told the Australian Broadcasting Corporation (ABC) the opposition's concerns about "labor provisions" were "greatly exaggerated".

Raby said by amending the terms of the agreement after they had been agreed upon could be dangerous.

"This is an agreement that's been negotiated over a decade, and it represents a very careful balance of interests," he said.

"Once you start to unpick one element of it, the thing will unravel."