WASHINGTON -- Sen. Rick Santorum yesterday wrote a letter to President Bush asking him to create an independent, non-partisan commission to objectively evaluate progress in Iraq.

The letter is a significant shift by the Pennsylvania Republican, whose stalwart support for nearly all aspects of the Bush administration's policies in Iraq could be a significant handicap in his race against state Treasurer Robert P. Casey this year if Pennsylvanians' support for the war continues to decline.

Mr. Santorum told the president that he was joining other members of Congress in their call for a panel that could "objectively and critically report" progress in Iraq to build Americans' confidence and trust in the mission.

Though the Senate passed legislation in November requiring more frequent and detailed reports on Iraq's reconstruction and military efforts, Mr. Santorum indicated yesterday that he did not think those reports, which will come from the administration, would provide what he views as the need for "an objective assessment."

"I believe that the American people have not received an accurate picture of America's successes and challenges in helping Iraq establish their democracy," Mr. Santorum wrote.

The White House had no comment on the letter.

The senator has occasionally questioned minor aspects of administration tactics in Iraq, but has more often laid blame for the public's falling support for the war with the press. He often criticizes reporters for not publicizing positive stories about the war and reconstruction effort, and in his letter to the White House, he added that the media has also "failed to fully address the consequences of failing on our mission in Iraq."

But in another notable sign that Mr. Santorum may be distancing himself from the White House as he campaigns for re-election, his letter includes several pointed references to the Bush administration's insularity in developing its Iraq policy.

In the letter's first paragraph, he congratulates the president for "reaching outside of your administration" by meeting yesterday with a bipartisan group of former secretaries of state and defense. Later, he argues that an independent commission could provide "an important new perspective on what needs to be done to ensure our success in Iraq."

Support for the decision to engage in the Iraq war dipped dramatically in Pennsylvania last year, along with Mr. Santorum's approval ratings -- which dropped to a new low in October but then rose in December, according to polls by the Quinnipiac University Polling Institute.