America is the world’s largest natural-gas producer, but New Englanders’ capacity to stay warm in winter may hinge on the fate of an expensive, 53-year-old import plant that its owner has threatened to shut down.

Constellation Energy plans to retire a Massachusetts power plant at the end of May. That will eliminate the biggest user of the liquefied natural gas, or LNG, that is imported through the company’s neighboring Everett Marine Terminal. Constellation said it is trying to line up new gas buyers to keep the terminal running. If it cannot, it will likely close the import facility as well.