LOS ANGELES Feb 13 (Reuters) - Sports Illustrated magazine on Monday unveiled its annual swimsuit issue with model Kate Upton on the cover in a two-toned, red string bikini with a bottom piece that, literally, appears to be little more than a string.

Upton, 19, a native of Melbourne, Florida, is the latest in a long line of models including Heidi Klum, Elle MacPherson, Tyra Banks and Brooklyn Decker, who have appeared in the coveted role as the swimsuit issue's cover girl.

M.J. Day , senior editor for Sports Illustrated, said Upton "embodies the sophistication and sexiness" called for in the issue that is seen by some 70 million readers in the magazine, the Web and on mobile devices like phones and tablet computers.

This year's 17 models in the swimsuit edition were photographed in Australia, Zambia, the Republic of Seychelles, Panama and in the United States in Apalachicola, Florida.

"Every single girl we shoot has the opportunity to be on the cover, and it really comes down to who has the best picture," Day told Reuters. "Whoever has that really special, jaw-dropping photo ends up on the cover."

Upton's picture certainly fits the bill. She is posed in the picture with one hand on her blonde hair and another on a bare hip. Her suit appears small on her voluptuous body -- but then again, it is a bikini.

The Sports Illustrated swimsuit edition, which hits newsstands on Tuesday, February 14, is annually the most widely-read edition of the magazine and being on the cover or inside its pages can launch a career for a model.

Inside the magazine are also star female athletes in nothing but layers of body paint. An iPhone app gives users a 360-degree view of painted women.

Model Bar Refaeli is pictured with sports stars Rafael Nadal, Chris Paul and Michael Phelps.

Last year's cover model, Irina Shayk, makes her sixth appearance in this year's edition. Among other models in the issue are Jessica Gomes, Genevieve Morton and Anne V. Jessica Perez, winner of the 2011 Rookie Model Search, also is featured. (Reporting By Bob Tourtellotte)

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