(Updates storm strength and location, weather conditions)

MEXICO CITY, July 12 (Reuters) - Tropical Storm Elida, which formed early on Saturday off Mexico's Pacific coast, could become a hurricane over the next two days, the U.S. National Hurricane Center said.

With maximum sustained winds near 45 mph (75 kph) and stronger gusts, Elida, the fifth tropical storm of the season, was located 235 miles (380 km) south of the popular resort of Acapulco and moving west-northwest at about 17 mph (28 kph), the NHC said.

"Strengthening is forecast during the next day or two and Elida could become a hurricane late Sunday or Monday," the Miami-based center said.

Skies were cloudy in Acapulco, Zihuatanejo and Puerto Vallarta, three of the most visited Mexican beach destinations on the Pacific, although waves were under three feet (one metre), according to the government's latest port data.

However, Mexico's national weather service warned that Elida could bring heavy storms across the southern states of Guerrero and Oaxaca over the next few hours. (Reporting by Cyntia Barrera Diaz; Editing by Eric Walsh)

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