UPDATE 1-Asia's Jan-Aug Iran oil imports fall 16 pct
* Top Asian buyers Iranian imports at 865,650 bpd in Aug, up 30 pct y/y
Jan-Aug Iran oil imports fall to 927,860 bpd vs 1.1 mln bpd year ago
* U.S.-Iran talks unlikely to lead to quick import boost
By James Topham
TOKYO, Sept 30 (Reuters) - Iran's top four crude buyers cut their purchases 16 percent in the first eight months of the year, with oil shipments likely to remain under pressure in coming months, despite tentative signs of better relations between Tehran and Washington.
The U.S. and EU sanctions aimed at curbing Iran's nuclear ambitions have forced China, India, Japan and South Korea to reduce their reliance on Iranian oil, trimming the OPEC nation's exports by more than half since early 2012 and costing it billions of dollars a month in lost revenue.
The European Union and the United States believe Iran is developing nuclear weapons, while Iran says its programme is for electricity generation.
On Friday, U.S. President Barack Obama and Iranian President Hassan Rouhani spoke by telephone, the highest-level contact between the two countries in decades and the culmination of a dramatic shift in tone that began in August.
Still, the squeeze on Iranian oil exports is unlikely to end soon as any talks between Tehran and Washington are likely to be slow, difficult and fragile.
The four major Asian buyers between January and August imported 927,860 barrels per day (bpd) of Iranian crude, down 16 percent from the same eight months in 2012, according to government statistics and oil tanker arrival schedules.
The four imported 865,650 bpd of Iranian oil in August, up nearly a third from a year earlier, the data showed. The big jump was mostly due to South Korea not taking any Iranian crude in August 2012 because of EU restrictions on shipping insurance.
U.S. and EU measures have made it difficult for China, India, Japan and South Korea to insure oil shipments and have forced them to find new ways to pay Tehran since the Middle Eastern nation has no access to international banking networks.
To win waivers from U.S. sanctions, the buyers must also continually reduce their shipments. Japan won its fourth six-month waiver at the beginning of September, while the other three will be up for a renewal of exemptions in early December.
Japan, the last of the four to have its oil import data available for August, shipped in 214,879 bpd, its trade ministry said on Monday. The nation's imports fell 2 percent year-on-year to 187, 860 bpd for the January to August period.
Japan's top buyer of Iranian crude, JX Holdings, is set to cut its annual contract for next year by nearly 20 percent with the Middle Eastern producer, an industry source told Reuters last week.
Friday's call between Obama and Rouhani came after earlier optimistic remarks by the new Iranian president, who said he wanted talks with major powers on Iran's nuclear programme to yield "tangible results" in a short period of time.
(Editing by Aaron Sheldrick and Tom Hogue)