The Trans-Pacific Partnership negotiations have just concluded and the parties are about to begin a very long process of ratification and implementation. Once all of that is complete, the TPP will be ready and willing to accept new members. There’s a pretty long list of countries ready to join.

The president called the TPP America’s chance to “write the rules” instead of China. That’s an unfortunately confrontational way to sell international commercial cooperation. Certainly, the TPP is an effort to circumvent gridlocked negotiations at the World Trade Organization and establish new norms while lowering trade barriers. It’s not clear yet whether the proliferation and growth of megaregional agreements like the TPP will help or hinder the broader and more valuable goal of global trade liberalization.

In practice, having America “write the rules” mostly means (1) lower tariffs; (2) more rules on things like intellectual property, state-owned enterprises, and labor and environment protection; and (3) less pressure to eliminate America’s own protectionist policies like outrageous farm subsidies, shipping restrictions, and abusive antidumping laws.

But if the TPP is going to be a vehicle for exercising American influence over global economic governance, it will surely need to expand beyond its current 12 members.

Since the negotiations concluded a few weeks ago, half a dozen governments in the region have expressed or reiterated their interest in joining the TPP. These include Indonesia, South Korea, Colombia, Thailand, the Philippines, and Taiwan. The fact that so many countries are eager to join an agreement they haven’t seen and had no role in drafting says a lot about the politics of international trade.

Once the TPP text is released, we will have a better idea of what these countries will be required to do to gain entry to the agreement. Will they need unanimous approval from existing members? Will they be required to accept additional obligations beyond the current text? Will Congress and other legislatures have to ratify each accession? The answers to these questions could have a big impact on the future of the global trading system.