By Miguel Angel Gutierrez and Mica Rosenberg

MEXICO CITY (Reuters) - Hurricane Jova gained speed on Monday as it headed for one of Mexico's busiest cargo ports and popular tourist resorts along the country's beach-lined Pacific coast.

Mexico's national weather service said Jova, a Category 3 hurricane, was set to be one of the most powerful storms to hit the country in the last four decades, based on current forecasts.

The storm, with top winds reaching 125 miles per hour, was about 195 miles southwest of the port city of Manzanillo late on Monday, the Miami-based National Hurricane Center said.

Jova is expected to make landfall late on Tuesday northwest of Manzanillo near the laid-back resort towns of Melaque and Barra de Navidad, on a stretch of coast dotted with fine beaches.

The center said Jova could become a Category 4 hurricane on the five-step Saffir-Simpson scale of intensity later on Monday or early on Tuesday. It is moving very slowly at just 6 mph, increasing the chance of severe damage once it makes landfall.

"We are feeling a bit of tension because the slow speed could be quite dangerous," an official at the Manzanillo port authority said.

Manzanillo, Mexico's main point of arrival for cargo containers, has been closed since late Sunday and about 13 container ships are stuck in the port.

An official said shipments that were held up because of the lock-down, included 15,000 tonnes of sugar from Colombia, 16,000 tonnes of imported rolled steel and a shipment of iron pellets for domestic use.

Manzanillo handles about 750 containers of cargo a month and ships goods including cars, car parts, cattle, minerals and tequila to Asian and North American markets.

ONE OF THE WORST

According to Mexico's national weather service, nine hurricanes have made landfall with maximum wind speeds of more than 125 mph since 1970, including Gilbert, which arrived in 1988 with top winds of 178 mph (287 kmph).

Mexico has issued a hurricane warning for 200 miles of coastline stretching south from Cabo Corrientes below Puerto Vallarta, a popular stop for cruise ships.

Hurricane-force winds were possible within the warning area by Tuesday afternoon. The storm is moving east and is expected to turn toward the northeast on Monday night, the NHC said.

Rainfall of up to 15 inches is forecast in parts of the states of Michoacan, Colima and Jalisco, possibly causing life-threatening flash floods and mudslides.

"A dangerous storm surge is expected to produce significant coastal flooding near and to the east of where the center makes landfall," the latest hurricane advisory said.

There was a 50 percent chance of another cyclone forming further south, near the Pacific coast of Guatemala, the center said. Mexico has no major oil installations in the Pacific.

(Writing by Krista Hughes and Elinor Comlay; Editing by Sandra Maler)