Japan and New Zealand reacted cautiously Friday after U.S. President Donald Trump signaled he might reopen talks on a Pacific Rim trade deal that he pulled the U.S. out of shortly after taking office.

Japanese officials said they welcome the move if it means that President Trump is recognizing the importance of the Trans-Pacific Partnership. New Zealand's trade minister said his country is not blind to the benefits of free trade with the world's largest economy, but U.S. participation remains theoretical.

"It's not yet clear how real it is, given the different views in the U.S. administration," Trade Minister David Parker said.

Japan and New Zealand are among 11 countries that signed the agreement last month after deciding to go ahead without the United States. The others include Australia, Brunei, Malaysia, Vietnam, Singapore, Canada, Chile, Mexico and Peru.

In a surprise step, President Trump asked his top trade advisers Thursday to take another look at TPP and whether a better deal could be negotiated. He has previously criticized multi-nation pacts, preferring to negotiate one-on-one with other countries. With congressional elections later this year, he now faces pressure from some Republican lawmakers anxious that his protectionist policies could spiral into a trade war with China that would hit rural America.

The president tweeted that he "would only join TPP if the deal were substantially better" than the one negotiated by his predecessor, Barack Obama.

Japan's trade minister, Toshimitsu Motegi, warned that it would be difficult to renegotiate, saying TPP is a well-balanced agreement based on the varying interests of the signatory nations.

"It is an agreement so delicate, like something made of glass," he said. "So, it will be difficult to take only parts of it and reopen negotiation, or change only parts of it."

Australia's ambassador in Washington, Joe Hockey, said his country would welcome the U.S. back into the pact, according to The Australian newspaper.

The 11-nation trade deal, which was renamed the Comprehensive and Progressive Agreement for Trans-Pacific Partnership after the U.S. withdrew, was signed in March but won't come into force until it's ratified by individual nations.

Parker said other countries have also expressed an interest in joining, including Colombia, South Korea and Britain.

New Zealand's liberal government, voted into power last year, has been more cautious about the deal than the previous conservative government. One change the new government made was to introduce new laws that will restrict the sales of New Zealand homes to foreign buyers, a provision Parker said would not change were the U.S. to join the pact.