SINGAPORE, June 19 (Reuters) - Asia-Pacific crude fell on Tuesday as ample supply of sweet grades and poor refining margins continued to depress the market. * TENDERS - Vietnam's PV Oil sold three cargoes of Chim Sao crude to load in August via a tender at lower premiums than the previous month, traders said. The cargoes were sold at about $6 a barrel above dated Brent, they said. Japanese refiner Taiyo Oil bought two cargoes to load on Aug. 7-11 and 26-30 while European trader Vitol bought the Aug. 17-21 cargo, the sources said. - Murphy Oil issued a tender offering 600,000 barrels of Kikeh crude for Aug. 9-14 loading. The tender will close on June 21 with bids valid until the same day's evening. - Taiwan's CPC is seeking sweet crude for August loading in a tender to close on June 19 with bids valid until two days later. * INDONESIA - Indonesia is seeking sweet crude for delivery in early August, but has limited its suppliers to national oil companies after a recent presidential decree, trade sources said. This move, the sources said, would leave out international oil companies and trading firms that actively trade in the West African grades Qua Iboe and Escravos regularly purchased by Indonesia. "Since the directive to limit oil purchases to primary sources is public knowledge, anyone deemed a plausible supplier by Indonesia would simply charge a premium knowing that Indonesia's hands are tied as to who they can get oil from," HS Yen, an oil analyst at FACTS Global Energy said. Petral, the trading arm of Pertamina, is in talks with national companies from oil producers such as Angola, Nigeria, Algeria and Azerbaijan to buy 1 million barrels of sweet crude for August delivery, the sources said. The August purchase will replace an Azeri Light cargo on suezmax MT Smyrni that was seized by Somali pirates in the Arabian Sea in May on its way to Indonesia. * MARKET NEWS - Nexen Inc plans an extended four-week maintenance turnaround at the 200,000 barrel per day Buzzard oilfield in the North Sea during the third quarter for the platform's five-year regulatory inspection, a spokesman for the company said. - Iranian insurance companies are ready to offer coverage for foreign oil tankers to continue shipping Iran's oil after a European Union ban comes into effect next month, the semi-official Fars news agency reported. CRUDE Price Prev Change AUG Brent 94.69 97.44 -2.75 AUG Brent/Dubai EFS DUB-EFS-1M 2.50 2.60 -0.10 PRODUCT CRACKS Price Prev Change JULY fuel oil crack -2.27 -1.51 -0.76 JULY gasoil crack 16.12 15.76 0.36 AUG naphtha crack -12.13 -12.27 0.14 COMPLEX REFINERY MARGINS Today 6.31 Last 5 days 6.22 Last 365 days 7.45

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