UPDATE 1-Mexico's main crude oil ports closed, one reopens

(Updates with one port reopening, Pacific one closing)

MEXICO CITY, March 8 (Reuters) - Two of Mexico's three main crude oil ports were closed to shipping for a second successive day as bad weather in the Gulf of Mexico caused big sea swells, the government said on Saturday.

The ports of Dos Bocas and Cayo Arcas were shut because of waves in the Gulf of up to 14 feet (4.2 meters), the transport ministry said.

The third main Gulf of Mexico oil port, Coatzacoalcos, reopened on Saturday afternoon, the ministry said. Together, the three terminals ship about 80 percent of Mexico's daily exports.

Mexico is the world's No. 9 exporter of crude oil, shipping an average of 1.7 million barrels per day in 2007. It is a top three supplier to the United States.

Mexico's crude exports have been repeatedly disputed in recent months by bad weather and storms in the Gulf, often with shipments halted for days at a time.

State-owned oil monopoly Pemex usually reschedules shipments as soon as the ports reopened so as to keep up its supplies to refineries.

Salina Cruz, Mexico's smaller oil port on its Pacific coast, closed to shipping on Saturday afternoon because of waves of up to 15 feet (4.5 meters), the ministry aid. Salina Cruz port ships to Asian markets. (Reporting by Chris Aspin, editing by Todd Eastham)