FACTBOX: President Obama's cabinet nominee problems

(Reuters) - President Barack Obama was hit on Thursday by another embarrassment over one of his Cabinet nominees when Republican Senator Judd Gregg withdrew from consideration as commerce secretary, citing policy differences.

Three weeks since taking office, Obama has not yet filled his 15-member Cabinet. The Senate has approved some of his nominees, such as Secretary of State Hillary Clinton, but others have run into trouble.

Here are the nominees who encountered problems:

* Gregg was Obama's second pick for commerce secretary after New Mexico Gov. Bill Richardson withdrew in the face of a legal inquiry. Obama spent nearly a month before choosing Gregg, a well-respected lawmaker and accomplished negotiator, who pulled out on Thursday, saying he saw "irresolvable conflicts" with the Democratic president.

* Former Senate Democratic leader Tom Daschle withdrew his name from consideration as Health and Human Services secretary on February 3 amid questions over tax errors that prompted him to pay $140,000 in back taxes. Obama still needs to nominate someone else to oversee the healthcare system.

* Obama chose Democratic Representative Hilda Solis of California for Labor Secretary. The Senate Labor Committee this week recommended that she be confirmed by the full Senate, after questions about her husband's unpaid business taxes had earlier put her confirmation hearing on hold.

* Nancy Killefer, Obama's choice to oversee budget and spending reform, withdrew on February 3 because of tax problems. She stepped aside the same day Daschle's withdrew.

* Timothy Geithner was confirmed as treasury secretary by a vote of 60-34 on January 26 despite questions about late payment of some taxes. He previously served as head of the New York Federal Reserve Bank.

(Compiled by Washington bureau; editing by Philip Barbara)