PIC: Megan Fox Poses in Bra and Panties in Latest Armani Ad

 Giorgio Armani

Megan Fox strips down to a lacy bra and panties for her latest Emporio Armani ads.

The newly-engaged actress' billboards will roll out in New York, L.A., London, Milan, Rome and Tokyo beginning this July. She'll appear in commercials this September.

PHOTOS: The steamiest summer romances

Fox, 24 — who recently announced she won't appear in Transformers 3 — next stars in Jonah Hex, out this Friday.

The new issue of Us Weekly reports that on-again beau Brian Austin Green popped the question — again! — in Hawaii June. 1. "Yes, she is engaged," her rep tells Us.

PHOTOS: Megan, Brian and other couples with big age differences

But in all the excitement, the happy couple somehow lost the ring, sources tell Us.

"I saw her jumping up and down," a witness says of the beachside proposal at the Four Seasons Hualalai hotel on the Big Island in Hawaii. "Later, I saw a half dozen staff sifting through the sand."

The 2-carat bauble is still missing.

"Security and maintenance staff spent a couple of hours looking for it," another source tells Us Weekly. "No one found it."

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