Some officials in South Korea say agreeing to the pipeline investment might placate the U.S., but Trump is still threatening tariffs.

Investors have balked at the project, stalling its progress. But under the threat of tariffs, Japan and South Korea have started exploring ways to invest in Alaska L.N.G.

Japan, South Korea and other countries want to partner with the United States in a "gigantic" natural gas pipeline in Alaska, U.S. President Donald Trump said on Tuesday, claiming they would invest "trillions of dollars each.