A Bush administration official has told reporters that White House budget director Rob Portman is resigning and will be replaced by former Iowa congressman Jim Nussle.

The official said President Bush will make a formal announcement later Tuesday. The source also said Portman, a former congressman from the U.S. state of Ohio, wants to return to private life.

Portman has spent the past year as budget director for the White House, and held the position of U.S. trade representative for the year before that.

His expected replacement, Nussle, unsuccessfully ran for Iowa governor in 2006. More recently he has served as an aide in Iowa to the presidential campaign of former New York City mayor Rudy Giuliani.

Some information for this report was provided by AP and Reuters.