But regardless of his decision, such a move would be hard to navigate. The remaining 11 countries have already reached their own deal. In order for the U.S. to re-enter, the countries may need to start negotiations from scratch, and it is unclear what, if any, conditions they would set in order for that to happen.

And Trump is unlikely to rejoin “without further concessions,” suggests The New York Times, which could further complicate matters, as Japan has reportedly already “given all the concessions it could.” Several of the countries might insist that the U.S. accept the existing agreement as a whole as a requirement for rejoining.

Government officials from the participating countries also do not seem too hot on the idea of the U.S. re-entering the TPP, citing in particular the difficulty of re-negotiating an agreement that already took years to finalize.

Yoshihide Suga, Japan’s chief cabinet secretary, reportedly compared the TPP to a “glasswork,” noting that “It’s difficult to bring part of the pact and renegotiate it,” as it’s already “well-balanced.”

Australia’s trade minister, Steven Ciobo, said that with a deal already in place, he “can’t see that all being thrown open to appease the United States.” And Jacinda Arden, the prime minister of New Zealand, said that “it’s not just a matter of slotting into an existing deal” and the U.S. rejoining would “trigger another process of engagement and negotiation.”

Yet some officials expressed more enthusiasm at the prospect. Taro Aso, Japan’s finance minister and deputy prime minister said that “if the news is true, we would welcome it.” And foreign minister Taro Kono went further, saying that the U.S. rejoining “would be great news,” but noted that the immediate priority is to bring the existing agreement into force as quickly as possible.

A spokeswoman for Singapore’s Ministry of Trade and Industry appeared similarly open to the U.S. rejoining, noting that the TPP was “designed to be an inclusive agreement, which is open to like-minded countries willing and able to meet its high standards.”

Whatever happens, the TPP countries would likely benefit from the participation of the U.S., as it remains the world’s largest economy. And for the U.S., it could help counteract the damage caused by the threat of a trade war with a rising China.