(Updates with background, quote)
WASHINGTON, March 31 (Reuters) - U.S. communications regulators voted along party lines on Monday to limit so-called joint sales agreements among broadcasters, deals that allow TV stations to share advertising staff, though promising to respond to any waiver request within 90 days.
The Federal Communications Commission approved, in a 3-2 vote, new rules that would count a broadcaster as having an ownership interest in any station where that owner sells 15 percent or more of weekly advertising time.
Broadcasters that currently have such deals get two years to divest or apply for waivers, for instance arguing that the joint sales sharing agreement has no influence on programming or actually promotes localism and competitiveness of local TV.
Democratic FCC Chairman Tom Wheeler has argued that such deals, known as JSAs, effectively constitute one TV station owning another and should be allowed only under specifically considered waivers.
But the broadcasting industry, with backing from Republicans in Congress and at the FCC, have pushed back, saying such arrangements are vital to financially strapped local TV stations, particularly in smaller markets.
The new rules could prompt divestitures from large TV station owners such as Sinclair Broadcast Group Inc or Nextar Broadcasting Group Inc.
Shares of TV station operators, including also Lin Media LLC and Gray Television Inc took a hit when Well Fargo cut its rating on some broadcast stocks as the FCC began deliberations on the new rules.
In the same 3-2 vote, the FCC also launched the 2014 quadrennial media ownership review, merging the unfinished 2010 review into the new one. The review keeps the current limit on one owner's controlling a major newspaper and TV station in one market and seeks comment on possibly relaxing those restrictions.
The commission on Monday also unanimously voted to prohibit two or more of top four broadcasters that compete against each other in the same market from banding together and jointly negotiating retransmission agreements with cable and satellite companies, expecting it to help lower fees for consumers.
(Reporting by Alina Selyukh; Editing by Doina Chiacu and Marguerita Choy)