SOUTH BEND (AP) — U.S. Rep. Joe Donnelly endorsed Barack Obama for president on Tuesday, extending Obama's lead among the state's superdelegates even though Hillary Rodham Clinton narrowly won the Indiana primary last week.

Donnelly, who had been uncommitted, said he believed the Illinois senator could help move the country past the politics of stalemate and gridlock.

"He can take us to a place of bipartisan cooperation. He can change the tone of Washington," Donnelly said in an interview. "He can provide leadership on gas prices and health care and job creation in Indiana. He can work hard to solve Iraq and Afghanistan. I think he can do it with Republicans and Democrats together."

Donnelly's decision gives Obama the support of six superdelegates from Indiana, while Clinton is being backed by Sen. Evan Bayh and three other superdelegates. Clinton won 38 pledged delegates in last week's Indiana primary and Obama won 34 pledged delegates, according to unofficial calculations by The Associated Press.

Donnelly, who is seeking re-election this year after winning his first term in Congress in 2006, said his backing of Obama was not a call for Clinton to give up her bid for the Democratic presidential nomination.

"Sen. Clinton is a tenacious fighter for the American people, and particularly for working families, but I believe Barack Obama is the president that we need at this moment in history," he said.

Two Indiana superdelegates — Reps. Peter Visclosky and Brad Ellsworth — remain uncommitted.

More than two dozen superdelegates across the country have endorsed Obama in the week since he routed Clinton in North Carolina and lost Indiana.

He erased her longtime advantage in superdelegates this weekend. Superdelegates are party leaders who attend the convention as delegates by virtue of their positions and are not selected in primaries and caucuses.

Donnelly said he did not announce his decision before the Indiana primary because he did not want to sway anyone's vote.

Voters in Donnelly's 2nd congressional district in northern Indiana favored Clinton over Obama by a 52 percent to 48 percent margin, said Butch Morgan, the party's district chairman. Clinton won statewide by about 14,000 votes out of more than 1.2 million cast.

Donnelly said he never planned to base his presidential delegate vote on the primary outcome in his district.

"I chose Obama because of his ability to bring people together," he said.