The Trans-Pacific Partnership (TPP), or Trans-Pacific Partnership Agreement, was a highly contested proposed trade agreement between 12 Pacific Rim economies: Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, Vietnam, and the United States. The proposal was signed on 4 February 2016 but not ratified, being opposed by many Democrats and Republicans, including both major-party presidential nominees, Donald Trump and Hillary Clinton. After taking office, the newly elected President Donald Trump formally withdrew the United States from TPP in January 2017, therefore the TPP could not be ratified as required and did not enter into force. The remaining countries negotiated a new trade agreement called Comprehensive and Progressive Agreement for Trans-Pacific Partnership, which incorporates most of the provisions of the TPP and which entered into force on 30 December 2018. 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. The original TPP contained measures to lower both non-tariff and tariff barriers to trade, and establish an investor-state dispute settlement (ISDS) mechanism. The U.S. International Trade Commission, the Peterson Institute for International Economics, the World Bank and the Office of the Chief Economist at Global Affairs Canada found the final agreement would, if ratified, lead to net positive economic outcomes for all signatories., while an analysis using an alternative methodology by two Tufts University economists found the agreement would adversely affect the signatories. Many observers have said the trade deal would have served a geopolitical purpose, namely to reduce the signatories' dependence on Chinese trade and bring the signatories closer to the United States. Membership Twelve countries participated in negotiations for the TPP: the four parties to the 2005 Trans-Pacific Strategic Economic Partnership Agreement and eight additional countries.