(Recasts with earlier landfall prediction)

MEXICO CITY, June 1 (Reuters) - Tropical Storm Barbara strengthened in the Pacific Ocean on Friday and was expected to make landfall near the border between Mexico and Guatemala on Saturday without becoming a hurricane.

Forecasters at the U.S. National Hurricane Center in Miami said Barbara was located 215 miles (350 km) south of the small oil port of Salina Cruz. The port remained open.

Packing sustained winds of 50 mph (85 kph), and higher gusts, the storm was located over warm water off Guatemala's southern coast and that of the neighboring Mexican state of Chiapas. It was seen making landfall some time on Saturday.

The center said expected heavy rainfall could lead to life-threatening flash floods and mudslides on either side of the Mexico-Guatemala border.

Mexican television pictures showed flooded city streets and swollen jungle rivers in areas in Barbara's path which have been pummeled with heavy rain.

Mountains run parallel with the coast in the important coffee-growing region spanning the border area, and heavy rainfall can often unleash fierce torrents. Swollen rivers ripped towns apart in the area in the 2005 hurricane season.

Barbara had been downgraded to a tropical depression late on Thursday but became stronger overnight.

Earlier predictions had Barbara developing into a hurricane over the weekend and barreling toward Mexican coastal resorts like Puerto Escondido, a major surfing spot. A tropical storm becomes a hurricane when maximum sustained winds reach 74 mph (119 kph).

In the Gulf of Mexico, Tropical Storm Barry formed on Friday, the first day of the Atlantic hurricane season, and was bearing down on Florida.

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