Oregon Rep. Greg Walden agreed to give up his spot on the House-Senate tax bill conference committee at the request of another Republican lawmaker who wanted to serve on it, according to a Walden aide.

Spokesman Justin Discigil said Friday that Walden surrendered his seat on the conference committee to Rep. Fred Upton, R-Mich., because of his legislative work on a proposal in the Senate bill: selling off oil from the strategic petroleum reserve to help raise money for tax cuts.

Walden is chairman of the House Energy and Commerce Committee while Upton chairs the panel’s energy subcommittee. The chair of the environment subcommittee, Rep. John Shimkus, R-Ill., is also on the panel working out differences on the sweeping tax-cut measure.

A statement from House Speaker Paul Ryan’s office on Wednesday said the energy and commerce members would negotiate oil sales and another much bigger issue: a Senate provision that would remove the mandate requiring individuals to have health insurance or face fines.

That raised questions about why Walden would take himself out of the picture in negotiating a key health care agreement — something his office didn’t respond to on Wednesday. At the time, there was also no explanation of who sought the change in membership on the conference committee.

Discigil said Friday that the energy and commerce members would only deal with the oil sales provision. The statement on Ryan’s website had been changed to say that the energy and commerce members would negotiate just the oil issue. 

Discigil said the health mandate issue would be negotiated by members of the House Ways and Means Committee, which has general jurisdiction over taxes. 

“Given jurisdictional implications of the Strategic Petroleum Reserve provisions in the tax bill,” Discigil wrote in a statement, “at Chairman Upton’s request, Chairman Walden opted to provide Mr. Upton the opportunity to serve as a conferee.”