The rise in sales to Iran’s main clients, mostly in Asia and including Turkey, comes after an agreement that eased some of the sanctions aimed at the Opec member’s nuclear programme. 

The November deal also freed up $4.2 billion in oil payments to Tehran, but it does not allow for shipments to increase.

To ensure sanctions are not breached, Washington could put more pressure on Iranian crude buyers to slash purchases in coming months to keep the average volume capped at the one-million-bpd mark, less than half pre-2012 levels.

In total, February crude loadings by Iran’s top four buyers – China, India, Japan and South Korea – rose to 1.16 mbpd versus 994,669 bpd lifted in January, according to a loading plan seen by Reuters.

Adding in oil lifted by Turkey – which came in at 105,824 bpd in January and 117,857 bpd in February – Tehran’s exports have busted the sanctions limits at least since November. The loading volumes exclude condensate, a light oil, that Iran exports to China and other consumers.

Ever since the 2012 sanctions were imposed, five buyers – China, India, South Korea, Japan and Turkey – have bought nearly all of Iranian crude exports.

The intake of Iranian oil by Asian buyers alone has topped 960,000 bpd since November, government and industry data has shown, and adding in an average 100,000 bpd of crude for Turkey, the exports have breached 1 mbpd at least since then. With January and February loadings – for February and March arrivals – also holding above one mbpd, according to the document seen by Reuters, exports look set to breach the cap for the first quarter of the year, allowing up to three weeks for shipments to China, Japan and South Korea.

China lifted 502,500 bpd in February, again taking its purchases back to pre-sanctions levels, and rivalling the 564,536 bpd that the nation’s refiners received in January.