Supporters say the TPP would make trade easier, create jobs in these countries. But critics say some of the requirements exist to help protect workers and the environment.
The 12 nations are responsible for about one-third of all world trade. They include Australia, Chile, Japan, Malaysia, Mexico, Peru, Singapore, Vietnam and the United States.
Negotiators are attempting to settle several disputes. Some nations are arguing over intellectual property rights for films and music.
Charles Boustany is a congressman from the American state of Louisiana. He notes that in 2011, trade exports and imports with TPP countries supported nearly 15 million jobs in the United States. The Trans Pacific Partnership is an attempt to increase trade by making rules similar from one nation to another.
Lori Wallach works with the American activist group Public Citizen. She says some government trade rules protect the environment and the health of workers and people who buy imported goods.
She says rules that make work conditions safe or protect health are under attack if they are defined as a barrier to the international trade.
Opposition from labor and consumer protection groups means the proposed deal faces an uncertain future in Washington. The agreement has to be confirmed by many national legislatures, including the U.S. Congress.
For VOA Learning Engish, I'm Carolyn Presutti.