Japan's bid to join the Trans-Pacific Partnership trade negotiations may make it easier for it to import liquefied natural gas from the United States, a prospect that is raising the hackles of environmental groups.

Japan, the world's largest LNG importer, said Friday that it wants to be included in the accord, which now encompasses 11 nations in Asia and the Americas. Bringing Japan into a free-trade agreement may boost companies trying to export natural gas from the U.S., according to Randy Bhatia, an analyst with Capital One Southcoast in Houston.

The Energy Department is reviewing 16 applications to build export terminals to ship supplies to countries that don't have free-trade agreements with the U.S. Among the companies seeking to export gas are Sempra Energy of San Diego and Dominion Resources Inc. of Richmond, Virginia. Cheniere Energy Inc. has won approval for a facility that would begin exporting in 2015.