TEHRAN, July 7 (Xinhua) -- U.S. sanctions against Iran's oil exports will weaken the Organization of Petroleum Exporting Countries (OPEC), a Petroleum Ministry official told state-run IRNA news agency on Saturday.

"Iran's oil will not lose its customers because a lot of companies are buying oil from the country," said Moayyed Hosseini Sadr, the ministry advisor.

"There might be a slight decline in Iran's oil sale, but different companies' secret purchase of Iran's oil can compensate it," he said.

However, if the United States keeps pressures to ban Iran's crude sales, "it would disrupt OPEC plans because Iran produces five percent of the world total oil output and this is a significant amount," he added.

"There will remain no such organization (as OPEC) in the future after continuation of the sanctions" against Iran, he was quoted as saying.

On June 26, the U.S. Department of State said that it has been pushing countries to stop importing oil from Iran by November. It said that the United States was "not granting waivers" to any country which was in business with Iran.

Following Trump's decision to quit the historic Iran nuclear pact on May 8, the United States vowed to re-impose sanctions lifted under the accord against Tehran and inflict punishments like secondary sanctions on nations that have business links with Tehran.

Firms that were doing business in Iran were given up to 180 days to wind up investments, otherwise, they risk huge fines, it said.

Washington's withdrawal from the landmark Iran nuclear deal was widely criticized across the world. And some of its major European allies have been working to prevent the 2015 deal from falling apart.

Oil prices rebounded strongly following the message from the U.S. Department of State.