(Recasts, adds hurricane warning, changes dateline from Mexico City)

ACAPULCO, Mexico, Aug 31 (Reuters) - Tropical Storm Henriette gathered strength off Mexico's Pacific coast on Friday, dumping rain on the resort of Acapulco and threatening hilly areas with mudslides and flash floods.

The Mexican government issued a hurricane watch near the port cities of Manzanillo and Lazaro Cardenas and a tropical storm warning from a remote national park in the coffee growing state of Oaxaca up the coast and past Acapulco.

The U.S. National Hurricane Center said Henriette was expected to become a hurricane during the next day or so, as it moves up the coast toward the Baja California Peninsula, popular with U.S. tourists.

Henriette is expected to pass about 100 miles (160 km) off the peninsula's coast on Tuesday, according to the Miami-based hurricane center.

On Friday, the center of Henriette was about 85 miles (135 km) south of Acapulco, moving northwest with maximum sustained winds of some 45 mph (75 kph), with higher gusts, it said.

The forecasters said Acapulco had experienced tropical storm force winds in the afternoon.

"Life-threatening flash floods and mudslides are possible. Acapulco has received almost 4 inches of rain during the past several hours," the hurricane center said.

Small villages and towns in the hills that rise behind many of Mexico's Pacific beach resorts are susceptible to landslides.

At least 10 people were killed when rains trailing Hurricane Dean pounded Mexico last week. (Additional reporting by Armando Tovar and Frank Jack Daniel in Mexico City)

AlertNet news is provided by