Tehran's oil exports have been limited since former U.S. president Donald Trump in 2018 exited a 2015 nuclear accord and reimposed sanctions aimed at curbing oil exports and the associated revenue to Iran's government.

Even so, exports have risen during the term of his successor President Joe Biden, Reuters reported.

Iranian crude exports exceeded 1.5 million barrels per day (bpd) in May, the highest monthly rate since 2018, according to Kpler, a provider of flows data. They were around 2.5 million bpd in 2018, before the U.S. withdrawal from the nuclear deal.

Iran said in May it has boosted its crude output to above 3 million bpd. That's about 3% of global supply and would be the highest since 2018, according to figures from the Organization of the Petroleum Exporting Countries (OPEC). A source familiar with the matter told Reuters earlier this month output was still at this level.

The International Energy Agency this week put Iran's May production at 2.87 million bpd, close to Iran's official figure.

The rise from Iran comes as OPEC+, which includes OPEC, Russia and other allies, is cutting output to support the oil market, where expectations that economic weakness will dent demand have pressured prices.

Other analysts say Iran's production and exports have risen. SVB International, a consultant, estimates crude production hit 3.04 million bpd in May, up from 2.66 million bpd in January. Exports of crude and condensate were 1.93 million bpd in May.

Growth outside OPEC+ core

OPEC+ agreed on June 4 a wide-ranging deal to limit oil supply into 2024. Iran is not required to make cuts as, together with Venezuela and Libya, it has an exemption. Nigeria is not exempt but has faced internal challenges in raising output.

Analysts at JPMorgan in a report this week said OPEC+ needed to cut more. They lowered their Brent oil-price forecast for 2023 to $81 a barrel from $90, saying rising supply was offsetting demand growth.

"Within the broader OPEC+ alliance, supply has been also rising outside the core members," the analysts at JPMorgan said, and revised up their production expectations for Venezuela, Nigeria and Iran by almost 600,000 bpd from November.

"Invariably, to make room for this supply growth, OPEC+ needs to cut more, were the alliance to adhere to the market management strategy."