FILE PHOTO: Democratic U.S. presidential candidate Senator Elizabeth Warren attends a town hall event in Fairfield, Iowa, U.S. December 15, 2019. REUTERS/Brenna Norman/File Photo

HOUSTON (Reuters) - Oil billionaire Harold Hamm, a supporter of U.S. President Donald Trump, invited Democratic presidential contender Senator Elizabeth Warren to visit Oklahoma’s oil and natural gas fields while she is in the state this weekend.

Warren, an Oklahoma native who has called for higher taxes on multi-millionaires and pledged to ban the technology underpinning shale wells, will be in Oklahoma City to meet voters on Sunday.

Hamm’s letter, sent to Warren on Wednesday, said technological innovations like fracking have made Oklahoma the third-largest oil-producing state and made the United States “an energy and economic superpower.”

“We were listening when you and your fellow members of the Democrat party have repeatedly said you would order an end to domestic development and production of oil and natural gas in the first weeks of your administration,” the letter said, referring to Warren’s proposal to ban fracking.

A spokeswoman for Warren, who was in Los Angeles on Thursday preparing for a Democratic party debate, did not immediately respond to a request for comment.

Fracking, which is primarily used in shale wells, forces water, sand and chemicals underground at high pressure to release trapped pockets of oil and gas.

Hamm last week disclosed he would step down as chief executive of Oklahoma-based Continental Resources Inc and become the company’s executive chairman. He was an informal adviser to Trump’s 2016 presidential campaign and was considered for a cabinet post.