Environmental Protection Agency Administrator Scott Pruitt has recused himself from litigation challenging former President Barack Obama's climate change agenda and environmental rules he had been a party to as attorney general of Oklahoma.

"I have conferred with the Office of General Counsel's Ethics Office and understand I must recuse myself from matters I have a financial interest, or a personal or business relationship," Pruitt wrote Thursday in a notice to the general counsel obtained by the Washington Examiner.

"I also understand that I have certain obligations to my state bar and also under the President's Ethics Pledge that I have signed," the statement added. "This recusal statement addresses all of my ethics obligations."

A number of Democrats had been pressing Pruitt to recuse himself during his long confirmation process. The pressure on him continued even after he was confirmed by the Senate, including earlier this week.

Pruitt noted that there is a one-year cooling off period from the time he resigned his post as Oklahoma attorney general to become EPA chief. He won't involve himself in matters directly tied to Oklahoma until February of 2018.

Pruitt also listed the cases in federal court where Oklahoma was directly involved that he will no longer be an active participant, including the Clean Power Plan, the centerpiece of President Obama's climate agenda, strict rules for controlling smog, litigation related to Volkswagen's emission violations, and a number of others.

President Trump has signed an executive order directing EPA to review and ultimately rescind the Clean Power Plan. Last week, the D.C. Circuit Court of Appeals agreed to halt its review of litigation Pruitt was involved in, giving the agency 60 days to conduct its review of the plan. The decision by the court was considered a major victory for the states involved in the suit and the Trump administration.

In total, Pruitt listed a dozen cases where he has recused himself.

"I understand that this commitment is longer than is required by the federal impartiality standards, but I am taking this action to avoid even the appearance of any impropriety under federal ethics or professional responsibility obligations," he wrote.