Third Watch

AGING HIPSTERS Kiss has joined Mick Jagger in announcing that they will not, as previously stated, be performing at the ''United We Stand'' benefit concert Sunday in Washington, D.C. The band said in a statement that Paul Stanley needs hip surgery, and though he had postponed the surgery in order to appear at the show, ''it became apparent that increasing pain and the possibility of further damage would not allow him to meet the intense physical demands of a Kiss performance.''

As for Jagger, his spokeswoman denied yesterday that he pulled out of the RFK Stadium show, since he never officially confirmed that he was in. She also denied reports that Jagger's absence has anything to do with possible bad blood between Jagger pal Paul McCartney, at whose ''Concert for New York'' fundraiser the Rolling Stone will perform the night before, and Michael Jackson, who has commandeered the D.C. show (its official title has been changed to ''United We Stand -- What More Can I Give'' to plug Jackson's yet-unreleased benefit single). Rather, she said, Jagger appreciated the invitation to sing in Washington but can't do so because of ''prior commitments.'' She said she waited so long to counter the announcement of Jagger's performance because she couldn't track him down to confirm his plans. For eight days?

LEGAL BRIEFS It may have taken the Sept. 11 attacks to get Congress to act on one of Hollywood's top economic issues, runaway production. The term refers to the practice of shooting movies and TV shows in countries like Canada, where labor and production costs can be much cheaper, taking jobs away from American actors and production crews. A bill to stem the practice through tax credits for all-domestic productions had been languishing in the House of Representatives, but the attacks have focused the House's attention on ways to boost America's economy. Legislators now believe they can get the runaway production bill, initially proposed as a stand-alone measure, attached to the big economic stimulus bill currently moving through the House....

The World Wrestling Federation is appealing a British court's legal smackdown requiring the WWF to give up its initials and the Web domain name wwf.com to avoid confusion with the World Wildlife Fund. The wrestling league calls the ruling an unfair restraint on its trade.

HITCHING POST Former ''Beverly Hills 90210'' siren Tiffani Thiessen is engaged to her live-in boyfriend of a year, Richard Ruccolo. The former ''Two Guys and a Girl'' star popped the question on Friday. The couple met when she guest-starred on several episodes of the ABC sitcom last year. It will be the first marriage for both Thiessen, 27, and Ruccolo, 29. No wedding date has been set.