The Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) continues to attract new applicants to a long and growing queue. Despite strong incentives for current members to seek new participants and growing interest from global participants, actually getting new members into the agreement is likely to be challenging.¹

South Korea, to take one example, has decided to continue studying the issue for longer after farmers appeared to be strongly opposed to joining.² Domestic considerations always present complicated issues for governments. In an increasingly contested global trade landscape, domestic factors can both push potential members into accelerating the process of joining and pull some potential members out.

Countries currently in the queue all have to navigate their own complex internal politics to reach the end of the accession process. Existing members will also need to work carefully to balance interests within the group with the likely demands coming from the countries seeking to join.

The original batch of countries looking to create a common trade and economic platform had a set of shared interests and common objectives. All were members of the Asia-Pacific Economic Cooperation (APEC), and all had years or even decades of experience working together on trade issues. These conditions are less likely to apply as the list of potential members expands outward.

The original Trans-Pacific Partnership (TPP) expanded from four members in 2009 to 12 before entering into force as the CPTPP in 2018 with 11 members.³ It grew to 12 with the addition of the United Kingdom and will be 13 once Costa Rica’s domestic ratification is concluded later this year. Uruguay is currently in negotiations for accession.

The list of applicant countries is long and growing. To join the agreement, the process starts with a formal letter of request to join. In the continuing absence of a CPTPP Secretariat, this letter is delivered to New Zealand as the Depository. Submissions are not publicly released, nor is any official record of the list of potential applicants available.

Nevertheless, the current queue includes China, Taiwan, Ecuador, the Philippines, Indonesia, the United Arab Emirates (UAE), Cambodia, and Ukraine.

To help members assess which of these candidates is “ready” to join, in 2023, the CPTPP put into place three “Auckland Principles.” These include a determination of whether the potential member is ready to commit to the high standards of the agreement, whether the applicant has demonstrated adherence to similar types of commitments in the past, and whether the applicant can be accepted by all existing CPTPP members by consensus.

If all three criteria are met, the candidate country is given a long questionnaire which includes providing details on existing policies and practices relevant to the agreement commitments. This document, which is also not publicly available, is then circulated to members who are able to submit written questions to the applicant.

Once the answers have been deemed satisfactory, CPTPP members can move the applicant to a new category by opening a Working Party. Uruguay is currently the only country with an active negotiation process underway.

In June 2026, CPTPP members invited three of the applicants (Indonesia, the Philippines, and the UAE) to proceed with preparatory discussions.⁴

Given the current state of global trade and economic disruptions, there are good reasons for countries to consider joining the CPTPP. Membership provides a greater degree of certainty and lowered risk of legal and regulatory changes.

The CPTPP agreement is comprehensive, including commitments on tariffs and goods trade, services and investment opportunities, rules governing intellectual property (IP) rights, digital trade and data flow promises, limited commitments on standards, and some pledges on labor and environment. Many of these provisions are to be updated by members as part of a general review that is currently ongoing under the 2026 Chairmanship of Vietnam.⁵

There are also very sensible reasons why CPTPP members would like to see the agreement expand. The business case for using the CPTPP grows as the membership increases. To cite just one example, any product made for a CPTPP member to fit the existing rules of origin in the agreement will receive duty-free or lowered tariffs in all CPTPP member markets without the need for remanufacturing to meet different rules of origin criteria.

This matters because current and future CPTPP members tend to be quite promiscuous, with multiple trade arrangements already in place between them. Singapore and New Zealand, for example, now have seven different trade deals: a bilateral, the Trans-Pacific Strategic Economic Partnership or so-called P4, the CPTPP, the ASEAN-Australia-New Zealand Free Trade Area (AANZFTA), the Regional Comprehensive Economic Partnership (RCEP), the Digital Economy Partnership Agreement (DEPA), and the Agreement on Trade in Essential Supplies (AOTES). Talks are also underway for a Green Economy Partnership Agreement (GEPA).⁶ ⁷

While Singaporean and Kiwi businesses can use whichever agreement works best for their circumstances, agreements that cover more markets can be significantly easier for companies to use with lowered compliance costs. Having more members included in an arrangement provides greater market benefits.

There are good reasons, then, to want to add more members to an existing agreement. But most of the countries in the current queue are not going to be easy to add.

The economic benefits to the existing grouping from the inclusion of some applicants to the CPTPP are quite mixed. Some have very small domestic markets, which limits the potential gains to be had by existing CPTPP members. Some have relatively open markets already. Some have very limited trade potential, either in general or with many of the CPTPP members who are increasingly globally dispersed.

Most of the applicants in line to join also have significant downsides. Several pose complex political challenges. Some also add competitiveness concerns for most members or for a subset. There will be sector-specific worries about future entries into the grouping.

The CPTPP has always been touted as a “gold-standard, high-quality” agreement. While there is a lack of clarity about exactly what these terms mean and whether the CPTPP does, in fact, deliver on this promise, it is certainly true that the deal does not allow the kind of exclusions or carve-outs that are possible in other trade arrangements.

The CPTPP essentially requires, for example, that all tariffs be cut to zero. Not all need to reach zero immediately, or on entry into force, but informal rules basically require at least 85% of tariff lines to be duty-free immediately. Timelines for the removal or reduction of all other tariffs are quite short — as little as seven years. This level of coverage is significantly different from most other trade arrangements that may include 80%–85% of tariff lines with some tariff reductions and some elimination of duties at the end of the full implementation period.

There are no exemptions in the CPTPP for developing countries. Some very specific provisions can be phased in for some members, such as some of the IP rules. Again, these timelines can be extremely short at 2–5 years. After these timelines expire, the full legal implementation of the specific provision is meant to be in place.

Existing CPTPP members have taken advantage of what are called “side letters” to address some specific issues. These letters have, for example, grandfathered certain bilateral trade commitments into the CPTPP. Some letters apply to more than one member, such as Vietnam’s time extension to implement the e-commerce chapter rules (now expired, but application is still uneven) or New Zealand’s exemption from the commitments of the Investor-State Dispute Mechanism with many CPTPP parties. In general, however, side-letter exemptions, exclusions, or revised commitments have been kept to a minimum.

There is nothing in the CPTPP that requires that these kinds of informal rules continue in place as the agreement expands. However, there is a strong reluctance on the part of existing members to allow substantial carve-outs or build in too much flexibility.

Yet a look at the applicant queue to join the CPTPP suggests that these rules will be severely tested. None of the prospective members have had experience dropping all tariffs to zero, or even come close to doing so in other arrangements. The services and investment provisions essentially require all sectors to be fully open to CPTPP firm participation. There are ample reasons to doubt that adherence to some aspects of the existing legal text will be fast or easy.

The CPTPP expansion process is also unnecessarily cumbersome and problematic.⁸ Each applicant has been receiving a bespoke process, which dramatically restricts the total number of potential candidates that can be considered at a time. It took more than two years to conclude talks with the United Kingdom. Costa Rica first submitted its petition to join in 2022, with talks substantially concluded in May 2026 and entry into force set for 2027.

This situation leaves the CPTPP accession process in an interesting bind. Despite clear incentives for expansion and a long and growing list of potential applicants, getting deals done with the current group of prospective members will not be easy. Even a rapidly shifting global trade and economic environment may not incentivize some participants to lift past objections or prepare to open previously closed markets.