WASHINGTON - Veteran Republican Sen. Arlen Specter disclosed plans Tuesday to switch parties, bringing Democrats closer to the 60-vote supermajority they need to push Barack Obama's agenda through the Senate.

"This is a painful decision," said Specter at a Tuesday afternoon news conference. "I know that I'm disappointing a lot of my friends and colleagues...the disappointment runs in both directions."

Specter would give Democrats and their allies at least 59 Senate seats. One vacancy remains from the state of Minnesota, where Democrat Al Franken holds a narrow lead in a race being disputed in courts.