National Farmers' Federation chief executive Tony Mahar "almost" fell off his seat when he heard the news US President Donald Trump is considering re-joining negotiations on the Trans-Pacific Partnership (TPP) trade deal.

Key points: Mr Trump made the comments to farm-state politicians in a White House meeting

Mr Trump made the comments to farm-state politicians in a White House meeting US farmers would get better access to overseas markets under the TPP

US farmers would get better access to overseas markets under the TPP Australia played a key role in resurrecting the trade pact earlier this year

Australia and a group of 10 other nations resurrected the trade agreement earlier this year, despite Mr Trump's decision to abandon the deal in early 2017 as part of his "America first" agenda.

Farm-state politicians in the United States said after a White House meeting with Mr Trump that his trade representative, Robert Lighthizer, and his new chief economic adviser, Larry Kudlow would be looking into the agreement.

The TPP would open more overseas markets for American farmers.

Mr Mahar said it would "send a really good message" if President Trump reversed his opposition to the deal.

"A country the size of America, and the optics of having the US actually sign on to an agreement which is in contrast to what they've done in the last couple of months in relation to increasing tariffs is quite significant," Mr Maher said.

But Mr Maher cautioned that Australian farmers currently have an advantage over their US counterparts which must not be eroded under any revision of the TPP.

"We wouldn't want them to waltz in and for our competitive advantage to be eroded," he said.

"We want to maintain a significant advantage in products like beef into the Japan market. It is worth about $2 billion."

Republican Senator for Nebraska, Ben Sasse, said he was sure there were a lot of particulars the US would want to negotiate.

"But the President multiple times reaffirmed in general to all of us and looked right at Larry Kudlow and said, 'Larry, go get it done'," Senator Sasse said.

Eleven countries signed the agreement last month.

Mr Trump's rejection of the deal rattled allies and raised questions about whether protectionism will impede US economic growth.

Kansas senator Pat Roberts, the chairman of the Senate Agriculture, Nutrition and Forestry Committee, said he was "very impressed" that Mr Trump had assigned Mr Kudlow and Mr Lighthizer "the task to see if we couldn't take another look at TPP".

"That certainly would be good news all throughout farm country," he said.

The discussions came during a meeting in which Mr Trump told farm-state governors and politicians that he was pressing China to treat the American agriculture industry fairly.

Midwest farmers fear becoming caught up in a trade war as Beijing threatens to impose tariffs on soybeans and other US crops, a big blow to Midwestern farmers, many of whom are strong supporters of Mr Trump.

Mr Trump has mused about re-joining TPP negotiations in the past but his request to his top aides shows a greater level of interest in re-joining the pact he railed against during his 2016 campaign.

During a February news conference with Prime Minister Malcolm Turnbull, Mr Trump raised the possibility of re-joining TPP if the negotiators offered more favourable terms.

In a CNBC interview in January, Mr Trump said, "I would do TPP if we were able to make a substantially better deal. The deal was terrible."

AP/ABC