A gas flare on an oil production platform in the Soroush oil fields is seen alongside an Iranian flag in the Gulf.

The Trump administration has cut down Iran's oil exports more quickly than many expected, but just days before a White House deadline, it is still a long way from achieving its stated goal of zeroing out Iranian oil sales.

Iran's oil exports have fallen by about a third in the five months through September. They tumbled by about 800,000 barrels per day since President Donald Trump announced in May that he was abandoning a nuclear accord with Iran and restoring wide-ranging sanctions on its economy.

Still, Iran was selling roughly 1.7 million to 1.9 million bpd of crude oil and condensate, a super light form of oil, in September, according to estimates by investment banks, tanker-tracking firms and the International Energy Agency.

That's down from a 2018 peak of 2.7 million bpd in June, according to ClipperData. In the first six months of the year, Iran was averaging 2.4 million bpd in shipments, S&P Global Platts Analytics estimates.

Some of Iran's biggest customers, including China and India, are expected to keep buying its barrels. The Trump administration has also indicated it will allow some countries to continue importing limited quantities of Iranian oil, but officials haven't disclosed which nations will receive waivers.

Along with China and India, countries like Turkey, Italy, Spain, Greece and Japan have kept purchasing Iran's crude. But analysts widely expect the losses to balloon to between 1 million and 1.5 million bpd by the end of the year.

"Iranian crude and condensate exports look set to finish October around a similar level to September, although we expect volumes to drop off next month as sanctions kick in and buyers dissipate," said Matt Smith, director of commodity research at ClipperData, a firm that tracks tanker traffic.

Petro-Logistics, another tanker-tracking firm, says Iran probably lost more than 100,000 barrels per day in October.

Trump is restoring sanctions first implemented by the Obama administration to isolate Iran from global markets over its alleged pursuit of nuclear weapons. Those sanctions, backed by the European Union and the United Nations, forced Iran to the negotiating table, where it agreed to limits on its nuclear program in exchange for sanctions relief.

After taking office, Trump failed to convince European allies to take a tougher stance against Iran and renegotiate the 2015 Iran nuclear deal. Instead, he pulled the United States out of the agreement, restored sanctions on Iran and threatened to lock foreign firms out of the U.S. market if they do business with Iran.

Trump gave countries six months to wind down their purchases of Iranian crude. State Department officials later told foreign nations they expected oil buyers to cut their purchases to zero by Nov. 4, surprising the market and sending oil prices higher.