BEIJING (Reuters) - China’s crude oil imports from Iran in September fell sharply from the same month last year in a sign that China has curbed its purchases from the Islamic republic as Washington prepares to re-impose sanctions on Tehran’s oil sector.

FILE PHOTO: An oil tanker is seen at a crude oil terminal in Ningbo Zhoushan port, Zhejiang province, China May 16, 2017. REUTERS/Stringer/File Photo

Data from China’s General Administration of Customs showed China brought in 2.13 million tonnes of Iranian crude oil in September, or 518,300 barrels per day (bpd), down 34 percent from 3.22 million tonnes last September,

Chinese customs made a surprise announcement earlier on Thursday on its website that it was making available to the public monthly data on the nation’s import and export of commodities, including country of origin for imports and country of destination for exports.

The customs office had previously provided such data for a fee but suspended this service in April.

China’s September Iranian arrivals tumbled from 3.28 million tonnes, or 798,423 bpd, in August, the data showed.

The Chinese customs data confirmed a previous Reuters report that Asian buyers including Japan, China and South Korea had curbed imports in September ahead of the U.S. reimposition of oil sanctions on Tehran on Nov. 5.

Bank of Kunlun Co, the key Chinese conduit for transactions with Iran, is also set to stop handling payments from Tehran under pressure of the renewed sanctions.

Over the first nine months of the year, China’s imports from Iran were at 24.49 million tonnes, still up 4 percent from the same period in 2017, the data showed.

As Iranian imports have dropped, shipments from the United States surged in September even as its trade war with the U.S. intensified.

The data showed China’s oil imports in September from the U.S. were 1.04 million tonnes, or about 253,000 bpd, up from 495,551 tonnes a year earlier.

Much of the surge was because of purchases by state oil major Sinopec, Asia’s top refiner, which buys about 80 percent of China’s U.S. imports, said a state oil official with knowledge of China’s U.S. oil imports.

U.S. imports in the January to September period reached 12.14 million tonnes, or about 324,600 bpd, up 150 percent the same time a year earlier, the data showed.

Sinopec earlier this year said it would triple its trading volumes of U.S. oil. However, imports from October are likely to fall because of concerns oil may be added to the tariff list.

“The numbers are largely in line up to September...though imports from October shall plunge because of the trade tension,” said the official.

China’s imports from Saudi Arabia, the de facto leader of the Organization of the Petroleum Exporting Countries (OPEC), also fell 12 percent to 3.78 million tonnes, or 919,800 bpd, in September.

Demand for top supplier Russian oil was robust at 6.8 million tonnes, or 1.65 million bpd, up from 1.54 million bpd a year ago.

(1 tonne = 7.3 barrels for crude conversion)