WASHINGTON (AP) - Veteran diplomat Christopher Hill on Tuesday won the support of Republican Sen. Richard Lugar to become the next U.S. ambassador to Iraq, even as other GOP senators bluntly urged President Barack Obama to reconsider his nomination.

Lugar's backing is considered crucial to Hill's nomination because it would provide other moderate GOP senators political cover to vote for him. Indiana's Lugar is the top Republican on the Foreign Relations Committee and widely respected on foreign policy matters.

Two administration officials said Tuesday they were counting on Lugar's support for Hill to overcome Republican opposition and secure the 60 votes that would ensure his confirmation. The Senate is divided, with Democrats typically able to count on 58 votes at most. The officials spoke anonymously because Hill was meeting with GOP senators on Tuesday.

Hill's nomination has been in trouble since last week, when several Republicans, including Sens. John McCain of Arizona, Sam Brownback of Kansas and Lindsey Graham of South Carolina, warned that Hill, a career diplomat, lacked enough experience in the Middle East.

Hill is best known for his role in the Bush administration as chief U.S. negotiator in disarmament talks with North Korea. The negotiations stalled on a technical issue and GOP critics said Hill was too willing to make concessions to the Communist regime.

One administration official said the White House might try to assuage other Republican senators' concerns about Hill by appointing one of their former colleagues, ex-Senate Majority Leader Bill Frist, as special envoy to Sudan.

Hill met privately on Tuesday with several senators, including Lugar, McCain and Brownback. McCain had no immediate comment after the meeting.

Brownback has been the most outspoken opponent of Hill because of a long-running dispute over how to handle human rights abuses by the North Koreans.

Following his Tuesday meeting with Hill, Brownback circulated a letter among his colleagues asking Obama to pull the nomination. Among those who signed the letter was Sen. Jon Kyl of Arizona, the second-ranking Republican in the Senate, and Sens. John Ensign of Nevada, James Inhofe of Oklahoma and Christopher Bond of Missouri.

Other Republican critics, including McCain, have focused on what they say is a lack of expertise on issues facing Iraq.

On Monday, Secretary of State Hillary Rodham Clinton dismissed that argument as baseless, pointing out that John Negroponte, who served as Iraq Ambassador during the Bush administration, did not have direct experience in the Middle East or Arabic language skills when he took the job.

McCain, Brownback and the other GOP senators opposing Hill had supported Negroponte's confirmation in a 95-3 vote.

Clinton also defended Hill's handling of the six-party talks with North Korea.

"It is our perspective that he made a lot of lemonade out of some pretty bad lemons, and he was able to get the North Koreans on record as agreeing to certain obligations," Clinton told reporters. "We now have to follow through on those obligations."