Harold Hamm's Continental Resources has signed a preliminary oil deal in Venezuela, the Wall Street Journal reported. The company, led by one of President Trump's closest allies in the U.S. oil industry, said it would explore one of Venezuela's undeveloped oil fields.

The agreement remains preliminary and further details were not immediately available. Venezuela holds some of the world's largest oil reserves but has seen production decline amid years of political and economic turmoil.

The move marks a notable step by a U.S. oil company into Venezuela's energy sector. Continental Resources, founded by Hamm, is a major player in U.S. shale oil production.