LOS ANGELES (Reuters) - U.S. first lady Michelle Obama made a surprise and unprecedented appearance on Sunday's Oscars telecast when she presented the award for Best Picture, the first time a president or first lady has ever presented an Academy Award.

Appearing live on screen from the White House in Washington, almost 3,000 miles from the Oscars ceremony in Hollywood, Obama praised the work of the movie industry before announcing the Iran hostage drama "Argo" the Best Picture winner.

Wearing a silver evening dress, Obama said this year's nominated films had "made us laugh, made us weep and grip our armrests just a little bit tighter."

Obama added: "They reminded us we can overcome any obstacles if we dig deep enough and hard enough. They are especially important for young people. Everyday they engage in the arts, they learn to open their imaginations ... and strive to reach those dreams."

"Argo" director and co-producer Ben Affleck said he felt like he was "sort of hallucinating" when Obama presented the award.

"The fact that it was the first lady was an enormous honor ... it was very cool," Affleck said backstage after collecting the Best Picture trophy.

(Reporting By Tim Reid and Nichola Groom; editing by Mary Milliken and Sandra Maler)