The United States has agreed to join Singapore, Brunei, Chile, and New Zealand in a free-trade agreement that could be the beginning of a broader Asia-Pacific free-trade zone, officials said. U.S. Trade Representative Susan Schwab is expected to announce Washington's decision to joint the Comprehensive Trans-Pacific Strategic Economic Partnership Agreement at a meeting Monday with trade ministers from the four countries on the sidelines of the U.N. General Assembly. The agreement—the first free-trade deal involving a group of Pacific countries—was signed between Singapore, Chile, and New Zealand in 2005. Brunei joined a year later. It was called the P4 group, with a broad objective to remove trade barriers among participants within a decade. New Zealand Prime Minister Helen Clark welcomed the U.S. decision to join the group, saying it would strengthen her country's economy. “It's very, very big news. It has to be remembered [that] the U.S. accounts for close to 10 percent of our total trade,” she told reporters Monday. “It's a huge economy. It's a growth engine of the world economy even in its slow times, and very important to us.” The U.S. decision to join the agreement will give momentum to a long-term initiative within the 21-member Asia-Pacific Economic Cooperation (APEC) to create a free-trade agreement. APEC, which includes the United States, China, Russia, Japan, Canada, Australia, and key Southeast Asian countries, accounts for nearly half of world trade.