Iranian authorities are trumpeting increased exports as it pushes to get a nuclear deal with western powers done.

National Iranian Oil Co chief executive Mohsen Khojasteh Mehr would not disclose numbers but told the domestic press over that the country was both selling its oil and receiving payment, even as the US keeps up its "maximum pressure" sanctions campaign.

"I am afraid I cannot reveal export figures but I can just say that the situation has improved," Mehr said.