Cheniere Energy Inc.’s expected $18 billion deal to supply natural gas to China signals the company’s growing bet on the country, and China’s emergence as a top market for U.S. gas exporters.

In a move that would be announced as part of a broader U.S.-China trade deal, China’s state-owned China Petroleum & Chemical Corp., known as Sinopec, will agree to a long-term contract to buy about $18 billion of liquefied natural gas from Cheniere, The Wall Street Journal reported Sunday.