Venezuela's state oil company said Friday that it will buy four oil tankers from Iran, expanding its fleet with the help of a nation closely allied with President Hugo Chavez. Petroleos de Venezuela SA said in a statement that its shipping subsidiary, PDV Marina, had signed a contract to buy the tankers from the Iran Marine Industrial Company. It did not disclose the price. PDV Marina president Asdrubal Chavez, who is a cousin of the president, said the deal is among various projects involving the two governments, and is also part of Venezuela's larger plan to expand PDV Marina's current fleet of 21 oil tankers. Venezuela is the world's fifth largest oil exporter. Although the US remains its top buyer of oil, Chavez has sought to diversify the country's clientele. The leftist president also has sought particularly close ties with Iran since he took office in 1999. Iranian investment in the South American country includes a tractor factory, plans for several housing projects and joint oil exploration.