Updated: 5:11 p.m.

Sen. Judd Gregg (R-N.H.) has withdrawn his nomination to be Commerce secretary in President Barack Obama’s administration, citing differences of opinion with the Democratic president.

Gregg was nominated a week ago to take the Commerce job, and if confirmed, would have been the third Republican to join the Cabinet. He was Obama’s second choice, after New Mexico Gov. Bill Richardson (D) withdrew his nomination over an ongoing government probe in his home state.

In a statement, Gregg thanked Obama for the offer to join the administration, saying: “This was a great honor, and I had felt that I could bring some views and ideas that would assist him in governing during this difficult time. I especially admire his willingness to reach across the aisle.

“However, 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. 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.”

Earlier this week, National Republican Senatorial Committee Chairman John Cornyn (Texas) indicated that even before Gregg was tapped as Commerce secretary, the New Hampshire lawmaker had decided against seeking re-election in 2010. It remains unclear whether Gregg’s decision to withdraw his nomination will change that decision.

New Hampshire Democratic Gov. John Lynch had indicated he would tap Republican Bonnie Newman to replace Gregg in the Senate once he won confirmation as Commerce secretary.

White House Press Secretary Robert Gibbs, in a statement Thursday afternoon, offered regret that Gregg “has had a change of heart.”

“Senator Gregg reached out to the President and offered his name for Secretary of Commerce. He was very clear throughout the interviewing process that despite past disagreements about policies, he would support, embrace, and move forward with the President’s agenda. Once it became clear after his nomination that Senator Gregg was not going to be supporting some of President Obama’s key economic priorities, it became necessary for Senator Gregg and the Obama administration to part ways.”