Iranian crude oil exports in January were higher than expected, while February shipments so far have been holding steady or even higher compared to last month, as several of Iran’s customers are using up their U.S. sanction waivers to continue importing Iranian oil, Reuters reported on Tuesday, citing industry sources and shipping data.

According to tanker-tracking data from Refinitiv Eikon and a source at a company tracking Iranian oil flows, Iran’s exports in February have averaged 1.25 million bpd so far, while the January exports were between 1.1 million bpd and 1.3 million bpd, higher than the previously expected below 1-million-bpd level, which was seen in December.

While tracking Iran’s oil exports has become an increasingly difficult task after the U.S. sanctions returned in early November, some of the key Iranian oil customers that received U.S. waivers resumed buying Iran’s oil in 2019 or increased imports to their respective ceiling allowed under the waivers, after an initial ‘wait-and-see mode’ for November and December purchases amid uncertainties who is getting waivers.

Iran’s key Asian customers—Japan, South Korea, India, and China—are all buying Iranian crude once again, but at much lower rates than they did before November when U.S. sanctions kicked in, S&P Global Platts estimates showed at the end of January.

According to the S&P Global Platts calculations, the rate at which India, Japan, and South Korea are importing Iranian crude at the moment, is at least half lower than the rate from before the sanctions went into effect.

India and China are Iran’s largest crude oil buyers, accounting for 80 percent of the country’s oil exports to Asia, which, in total, constituted half of Iran’s overall oil exports. Now, as the sanction waiver window narrows, S&P Global Platts analysts expect Iran’s oil exports to fall to 1.2 million bpd over the first four months of 2019, and further slump to 860,000 bpd in the fourth quarter of the year. This compares with an average 2.7 million bpd in the first few months of 2018, before President Trump pulled the United States out of the so-called Iran nuclear deal last May.

As the ‘waivers window’ will be shrinking ahead of the end of the 180-day waiver period in early May, buyers could be rushing to buy what they can before April in order to be able to complete transactions before May in case waivers are not extended, according to analysts.

The U.S. has signaled that Iranian customers shouldn’t rely on waivers extensions, but the Trump Administration has not yet officially said if it would stop granting waivers. Some observers say that the decision would depend on the price of oil at the time the U.S. needs to decide about exemptions, because, despite the pledge for ‘zero’ Iranian exports, the Administration will not be willing to drive up oil prices too high.