(Adds details of deal)

By Steve Gorman and Kemp Powers

LOS ANGELES, Feb 10 (Reuters) - Union leaders for striking Hollywood writers voted on Sunday to formally endorse a deal with studios to end their bruising three-month-old labor clash, calling an immediate halt to picketing and paving the way for writers to return to work by mid-week.

The unanimous approval of the deal by the governing bodies of the Writers Guild of America came a day after the union and studios finalized details of a settlement hinging on how much writers should be paid for work distributed over the Internet.

While WGA leaders acknowledged the agreement falls short in some areas, they emphasized it avoided any of the rollbacks initially sought by studios and made key, if modest, gains in the burgeoning arena of new media.

"This is the best deal this guild has bargained for in 30 years, after the most successful strike this guild has waged in 35 years," WGA West president Patric Verrone said at a news conference announcing the outcome of the board action.

Union leaders said they were pulling the plug on further picketing, which has become an almost daily occurrence outside many of the studios and production facilities around Los Angeles and New York.

But the 10,500 film and TV writers who walked off the job on Nov. 5, shattering 20 years of Hollywood labor peace, are not expected to officially return to work before Wednesday.

That's because the governing boards of the East and West Coast branches of the union opted to wait for members to vote on the plan themselves before the strike is officially lifted.