Oscar-winning quartet George Clooney, Meryl Streep, Reobert De Niro and Tom Hanks are urging the

Screen Actors Guild to quickly start its contract negotiations with Hollywood producers in order to avoid another strike.

The Hollywood stars placed an ad in the Thursday edition of trade papers Daily Variety and the Hollywood Reporter two days after the Writers Guild of America ended a three-month strike, which SAG strongly supported. The ads urged SAG leaders to commit to negotiating a deal quickly, the Daily Variety said.

To date, studios have put feature development on hold until SAG signs a new deal. The SAG contract is set to expire on June 30, but talks have not yet been scheduled. SAG's committee on wages and working conditions said they have been preparing for the talks with the Alliance of Motion Picture and Television Producers, the studios' bargaining arm.

The last major SAG strike lasted for three months in 1980.

As proud members of SAG, we have seen the effect of a long-running strike on our community, the ad reads. Now that the writers have agreed to a deal, our hope is to get people back to work.

The ad, which ends with the stars' names, continues: Issues are important...Nothing can be solved until both parties agree to sit down together...There is too much at stake to wait.

SAG national executive director Doug Allen, which represents about 120,000 actors, said last Wednesday that the guild is still getting input about from its members and from negotiating partner AFTRA.

''This process will conclude in the March,'' Allen said in the statement. ''We will bargain with management at a time that will most benefit our members.''

Speaking at the Oscar nominee's lunch last week, Clooney expressed concern that some in the guild think that delaying talks increases negotiating power: ''I think there's a lot of strike fatigue, and I think you actually start losing negotiating power,'' he said.

''I would hope we in the Screen Actors Guild get back to the table, he added. Clooney is up for Best Actor for his role in Michael Clayton.