Lieberman said Sunday while on ABC's "This Week with George Stephanopoulos" that the presumptive Democratic presidential candidate has not been consistent on how to best deal with the war in Iraq.

"Senator Obama has been shifting. And I want a president who's going to be true to what he believes is best for our country," said Lieberman, a strong backer of Sen. John McCain of Arizona, the likely Republican nominee.

Meanwhile, former U.S. Rep. Bob Barr, R-Ga., told Stephanopoulos he sees both Obama and McCain as very "status quo" based on their political stances.

"Each in their own way is very much a creature of the status quo. Even though Senator Obama talks about change, the fact of the matter is that he is very wedded, if you look at his programs in terms of socialized medicine and healthcare," Barr said. "Senator McCain, of course, very much in (the) mold of George W. Bush in terms of more wire-tapping and assaults on individual liberty."