GENEVA (Reuters) – OPEC tries to depoliticise oil, the producer group’s secretary-general was quoted by the Iranian oil ministry as saying on Thursday, following accusations by Iran that the United States is using oil as a weapon against Tehran.

The United States has demanded that buyers of Iranian oil stop purchases by the start of May or face sanctions, ending six months of waivers that had allowed OPEC member Iran’s eight top customers, most of them in Asia, to import limited volumes.

Iranian Oil Minister Bijan Zanganeh warned on Wednesday that nations that use oil as a weapon will bring about the collapse of the Organization of the Petroleum Exporting Countries.

OPEC Secretary-General Mohammad Barkindo said at an oil and gas exhibition in the Iranian capital that “OPEC tries to depoliticise oil”, Iran’s oil ministry reported on Twitter.

“I have told my colleagues at OPEC that you must leave your passports home when coming to this organisation,” Barkindo was quoted as saying.