WASHINGTON - Several officials say veteran Republican Sen. Arlen Specter of Pennsylvania intends to switch parties, advancing his own hopes of winning a new term next year while pushing Democrats one step closer to a 60-vote filibuster-resistant majority.

The sources said an announcement could come later today or Wednesday. The officials who provided the information did so on condition of anonymity, saying they were not authorized to discuss his plans.

Specter is a 79-year-old veteran of five Senate terms, and one of only a handful of moderate Republicans left in Congress in a party made up largely of conservatives.