LOS ANGELES (Reuters) - The cast of the 1970s crime caper "American Hustle" grooved its way to the top prize from theScreen Actors Guild on Saturday in a key test of the film's Oscar mettle six weeks ahead of a likely competitive race for Academy Awards.

"American Hustle" from director David O. Russell has been hailed for its performances, although it won no individual acting awards on Saturday and only Jennifer Lawrence was nominated for her supporting role. It prevailed over another presumed Oscar front-runner, "12 Years a Slave," which only took home a best supporting actress trophy.

Australian Cate Blanchett won best actress for her role as a socialite who suffers a breakdown in Woody Allen's "Blue Jasmine," while best actor went to Matthew McConaughey for his turn as an unlikely AIDS activist in "Dallas Buyers Club.

Both actors are the clear front-runners for best acting Oscars after winning Golden Globes last Sunday. Screen Actors Guild (SAG) awards are honors that actors relish, however, because they come from their peers.

In what is widely considered one of the best years for quality film in recent memory, SAG and other guild awards to be handed out in the next two weeks could collectively steer the race in favor of one film for the industry's highest honor, the best picture Oscar, on March 2.

The SAG ceremony is one of the most closely watched of the Hollywood awards season because it makes up the largest voting group or around 20 percent of the 6,000 members of the Academy of Motion Picture Arts and Sciences that vote for the Oscars.

Bradley Cooper accepted the best ensemble cast award on behalf of a lineup that included Christian Bale and Amy Adamsin addition to Lawrence. All four of them are nominated in the four acting Oscar categories, a repeat feat by Russell after his hit last year "Silver Linings Playbook."

"He is an actor's director," said Cooper. "That notion is tossed around; he is the embodiment of it. He's the reason why all of us wanted to become actors when we were children."

UPSET IN SUPPORTING ACTRESS

"American Hustle" is a romp through loose 1970s New York and tells the story of petty con-artists who are caught and forced to collaborate with the FBI in a sting operation, inspired by the real-life Abscam case.

It won 10 Oscar nominations on Thursday, co-leading the field with space thriller "Gravity," basically a one-woman show starring Sandra Bullock as a stranded astronaut that is most recognized for its technical innovation.

But it is the small film that cost $4 million, "Dallas Buyers Club," that has done best in individual acting awards this week.

McConaughey's co-star Jared Leto won best supporting actor for his turn as his transsexual side-kick Rayon. Both he and McConaughey, who plays a homophobic Texan who gets AIDS and fights for treatment, impressed the film world with their extreme weight loss for their roles

"There's a magic place that we, as actors, can get or at least strive to get to. And you know we always don't get there. But, boy, when we touch it, it's magic," McConaughey said in recognizing the much ballyhooed ascent in his career.

In the supporting actress category, Kenyan actress Lupita Nyong'o of "12 Years a Slave" won in an upset over Lawrence who took the Golden Globe for her "American Hustle" role as a loopy wife.

Nyong'o is also nominated for an Oscar for her role as the hardworking slave Patsey in the brutal depiction of pre-Civil War American slavery "12 Years a Slave," which has a total of nine nominations, including best picture.

"Thank you, thank you, thank you Steve McQueen," Hollywood newcomer Nyong'o said to the British director who chose her after auditioning 1,000 actresses.

"Thank you for taking a flashlight and shining it under the floorboards of this nation and reminding us what it is we stand on."

MIXED RECORD ON OSCARS

In the last decade, the SAG awards have a mixed record on predicting the Oscar best picture with their choice of best ensemble cast for film. They have correctly predicted the Oscar in six of the last 10 years.

For best actor, they have tipped the Oscar winner in all of the last nine years, and for best actress, they have predicted six out of the last nine.

The Producers Guild of America, which will hand out their awards on Sunday night, has correctly selected the best picture Oscar winner with their outstanding film producer prize for the last six years.

But it is an abnormally long lead-in to the Oscars, and Academy members have almost a month before voting starts on February 14 and ends on February 25. The long wait adds to the uncertainty of the race.

In a bit of unscripted drama, actress Rita Moreno, 82, received the lifetime achievement award from the Screen Actors Guild on Saturday and dropped an expletive as soon as she hit the stage to accept the honor from actor Morgan Freeman.

Soon after, she said, "I am sorry about that word. Actually I am not."

The SAG honors are chosen by some 165,000 actors working in the United States and also reward acting in television drama and comedy as well as stunt work.

ABC's long-running success "Modern Family" won best ensemble in a comedy series, while the AMC Emmy winner "Breaking Bad" took the same prize for drama, the first SAG cast win for the show that ended last year.