The TPP began as an expansion of the Trans-Pacific Strategic Economic Partnership Agreement (TPSEP or P4) signed by Brunei, Chile, New Zealand and Singapore in 2005. Beginning in 2008, additional countries joined the discussion for a broader agreement: Australia, Canada, Japan, Malaysia, Mexico, Peru, the United States, and Vietnam, bringing the negotiating countries to twelve. In January 2017, the United States withdrew from the agreement. The other 11 TPP countries agreed in May 2017 to revive it and reached agreement in January 2018. In March 2018, the 11 countries signed the revised version of the agreement, called Comprehensive and Progressive Agreement for Trans-Pacific Partnership. After ratification by six of them (Australia, Canada, Japan, Mexico, New Zealand and Singapore), the agreement came into force for those countries on 30 December 2018.