US President Donald Trump is reconsidering joining the Trans-Pacific Partnership (TPP), a trade agreement that he campaigned vigorously against in his presidential race and withdrew the US from just days after taking office.

Nebraska Republican Senator Ben Sasse said in a statement Thursday that it is good news that Trump has directed White House National Economic Council Director Larry Kudlow and US Trade Representative Robert Lighthizer to negotiate a US entry into the TPP.

Sasse was among a group of US lawmakers and governors from farm states meeting Trump at the White House on Thursday.

White House spokeswoman Lindsay Walters later confirmed the message by saying: "The president has consistently said he would be open to a substantially better deal.

"To that end, he has asked Ambassador Lighthizer and Director Kudlow to take another look at whether or not a better deal could be negotiated," Walters said.

The TPP was a free trade agreement among 12 Pacific Rim nations that former US President Barack Obama pushed aggressively as the core of a rebalance to Asia strategy and a geopolitical tool against China's growing clout in the region. Many economists believe TPP's economic benefits to the US are limited.

After Trump withdrew the US from the TPP talks, the other 11 countries moved ahead to forge their own agreement by cutting some key provisions insisted on by the US earlier, on such issues as intellectual property, procurement and investment.

The new agreement, known as the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP), was signed on March 8 in Chile by Australia, Brunei, Canada, Chile, Malaysia, Mexico, Japan, New Zealand, Peru, Singapore and Vietnam.

The 11 countries, with a total population of 498 million people and average per capita income of $28,090, represent 13 percent of the global economy.

Chilean President Michelle Bachelet said in March that if the US wants to rejoin, it would have to do so under the TPP-11 terms. Her words came after Trump suggested that the US could rejoin TPP "if we were able to make a substantially better deal".

Trump and three other key presidential candidates - Hillary Clinton, Bernie Sanders and Ted Cruz - all opposed the TPP in their 2016 campaigns in a bid to win support from unions, which are overwhelmingly against trade deals. Trump has repeatedly described TPP as a "terrible" deal and said he prefers bilateral deals instead of multilateral deals.

AFL-CIO President Richard Trumka said on Thursday that "TPP was killed because it failed America's workers and it should remain dead. There is no conceivable way to revive it without totally betraying working people," he said in a tweet.

China is not part of the TPP. But China is negotiating the Regional Comprehensive Economic Partnership (RCEP) with 10 ASEAN nations and Japan, South Korea, Australia, New Zealand and India.

The 16 nations hope to conclude the deal by the end of this year. RCEP covers 3.4 billion in population and about 30 percent of the world's GDP.

China is the largest trade partner for most members of RCEP and TPP.