Australia was quick to welcome US President Donald Trump's casual comment that the US might be prepared to join the Trans-Pacific Partnership if a "substantially better" deal could be struck.

Yet while making it clear that we would welcome US participation on the terms already negotiated, Australia needs to clarify that these terms are not open to renegotiation to shift the balance of benefits further in America's favour.

Some elements of the TPP fit the standard free trade agenda, and should be in each member's self-interest. There are also many "behind-the-border" issues that favour one party over another – intellectual property (IP) is the clearest example. While America is a big net exporter of IP, Australia is a net importer. Rules that grant more comprehensive IP protection therefore benefit the US and harm Australian consumers and researchers. Investor-state dispute settlement (ISDS) is another example.

Negotiations that enhance trade openness would be fine, but it is clear this is not what Trump (or his supporters) have in mind when he talks about "this horrible deal". If Australia accepts the idea of renegotiation, we would find ourselves in the same position we were in with the AustraliaUS Free Trade Agreement and the TPP before Trump pulled out. Political imperatives would make signing up to the renegotiated terms inevitable: not signing up with our closest and largest ally because of some obscure IP or ISDS issue is impossible to contemplate.

Australia needs to make its position clear at the earliest opportunity. New members are welcome in the TPP, but the hard horse-trading has already been done and we're not ready to give away any more. If you want to join a club, you can't insist on self-interested alterations to the membership rules beforehand.

Japan's parliamentary spokesperson Yasutoshi Nishimura has made this explicit on Japan's behalf. Ideally the 11 members of the deal should be lobbied to support this position collectively. But if some countries are reluctant, Australia should reinforce the point, together with any like-minded prospective members.