President Obama’s choice for Commerce Secretary, Senator Judd Gregg, withdrew his nomination on Thursday. He said there were “irresolvable conflicts” between him and the administration.

“It has become apparent during this process that this will not work for me as I have found that on issues such as the stimulus package and the Census, there are irresolvable conflicts for me,” Mr. Gregg said in a statement. “Prior to accepting this post, we had discussed these and other potential differences, but unfortunately we did not adequately focus on these concerns. We are functioning from a different set of views on many critical items of policy.”

The withdrawal comes one week after Mr. Gregg was named to become the third Republican member of the Obama Cabinet. It is the second time that the Commerce Secretary position has been vacant within the last month.

Mr. Gregg, a Republican of New Hampshire, had not resigned his seat in the Senate. He has been away from the Senate floor this week, presumably preparing for his confirmation, and did not vote on the administration’s economic stimulus plan.

In announcing his selection as Commerce Secretary last Tuesday, Mr. Gregg stood at Mr. Obama’s side during a brief White House ceremony. The president touted his nominee as a fiscal conservative who could help “shore up our financial system and revitalize our economy.”

The president selected Mr. Gregg exactly two months after he nominated his first choice for commerce secretary, Gov. Bill Richardson of New Mexico. He withdrew his name from consideration because of a federal investigation into state contracts, the first of several controversies surrounding the president’s top nominees.

In announcing his withdrawal, Mr. Gregg released a statement through his Senate office. It was not announced by the White House, though aides said the president had been informed of Mr. Gregg’s decision.

“Obviously the President requires a team that is fully supportive of all his initiatives,” Mr. Gregg said in a statement. “I greatly admire President Obama and know our country will benefit from his leadership, but at this time I must withdraw my name from consideration for this position.”

He added, “As a further matter of clarification, nothing about the vetting process played any role in this decision. I will continue to represent the people of New Hampshire in the United States Senate.”

It was another blow for the White House, which has seen three Cabinet nominees withdraw from consideration. Tom Daschle pulled his name from consideration to lead the Health and Human Services Department amid questions about his tax returns.