INDIANAPOLIS - Former Indiana Rep. Lee Hamilton is backing Sen. Barack Obama in an endorsement that could boost the presidential hopeful's national security standing, The Associated Press has learned.

Hamilton, who during a three-decade House career rose to be chairman of the Foreign Affairs and Intelligence committees, also was vice chairman of the Sept. 11 commission. He planned to announce his endorsement of Obama on Wednesday.

In an interview Hamilton said he viewed the Illinois senator as a champion of "the politics of consensus and not of partisan division."

"I think he is driven by the search for the common good," Hamilton said.

Hamilton is best known as the top Democrat on the panel that investigated the 9/11 terrorist attacks. He also was co-chairman of the Iraq Study Group, a bipartisan commission that assessed U.S. policy in Iraq.

Although Hamilton is not a Democratic superdelegate, his backing comes on the heels of several high-profile endorsements for Obama, who leads Sen. Hillary Rodham Clinton in delegates for the party's nomination. Sens. Bob Casey Jr. of Pennsylvania and Amy Klobuchar of Minnesota endorsed Obama in recent days.

Hamilton is the highest-profile Indiana Democrat to back Obama before the state's May 6 primary. Sen. Evan Bayh and the bulk of Indiana's Democratic Party leadership have campaigned actively for Clinton in a state where neither candidate is regarded as a natural front-runner.

Hamilton, once mentioned as a possible running mate for Bill Clinton, told the AP he believed Obama was the candidate most likely to unite the country.

"I begin by asking myself what kind of leadership the country needs at this juncture and I think, for me at least, the answer is that you want a candidate that will try to bring together a country that is very evenly divided, a country in which partisanship has been very sharp and to try to get a candidate who will create a new sense of national unity and will try to transcend the divisions within the country," he said.

Hamilton spent 34 years in Congress representing a southern Indiana district before retiring in 1999.

Hamilton now leads the Woodrow Wilson International Center for Scholars in Washington. In a speech there last year, written by a longtime aide to Hamilton, Obama warned Pakistan that he would use military force if necessary to root out terrorists.