10:00 AM PT -- Despite the massive rock, Sofia's rep released a statement saying, "As of today, Sofia is not engaged."


"Modern Family" hot mama Sofia Vergara celebrated her big 40th birthday on Tuesday by rocking a sexy bikini in Mexico ... and flashing what is reportedly her new giant engagement ring.

Sofia's on-again-off-again businessman boyfriend Nick Loeb reportedlypopped the question this week and gave her the huge bling during their vacation with pals on the Riviera Maya.

Sofia -- who dated Tom Cruise back in 2005, before the whole Katie Holmesthing -- has a son from a previous marriage. 

From TMZ.com

Thumbnail via TMZ.com