Recasts to focus on nickel's fall; updates prices by Asian market close

May 21 (Reuters) - Nickel declined on Thursday as investors assessed the supply of the metal and a new policy of top producer Indonesia to put exports of some nickel products under state control.

The benchmark three-month nickel CMNI3 on the London Metal Exchange declined 1.39% to $18,665 a metric ton as of 0800 GMT.

The most-active nickel contract SNIcv1 on the Shanghai Futures Exchange declined 1.23% to close at 142,770 yuan ($20,986.33) a ton.

Some details of the policy, announced by President Prabowo Subianto on Wednesday, were unveiled on Thursday by officials of the trade ministry and the chief executive of Indonesia's sovereign wealth fund, Danantara. A unit of the fund will become the sole exporter of palm oil, coal and ferroalloys as soon as September 1.

Ferronickel, whose HS code covers nickel pig iron, will be put under the oversight of the state export body. It is a key feedstock for stainless steel and accounts for the majority of Indonesia's nickel output.

Traders noted that nickel stocks SHFE NI-STX-SGH are still on the rise, and are at the highest since May 2017. LME nickel inventories MNISTX-TOTAL also ticked higher as of Tuesday.

Meanwhile, implementation of the new policy is in focus, with some investors saying it could prove impossible to implement as they question how a single company could manage exports to a vast number of downstream buyers across the globe.

The U.S. dollar =USD and oil LCOc1 ticked higher, as President Donald Trump said the U.S. was willing to wait to get the right peace deal with Iran in the final stages of negotiations, weighing on industrial metals led by copper.

London benchmark copper CMCU3 tumbled 1.21% to $13,490 a ton, and the Shanghai most-active copper SCFcv1 closed 0.38% higher at 103,940 yuan, after a 1.97% rise earlier this session.

Elsewhere on the LME, aluminium CMAL3 dipped 0.28%, zinc CMZN3 dropped 0.75%, lead CMPB3 nudged 0.08% higher and tin CMSN3 slid 1.93%.

Among other SHFE metals, aluminium SAFcv1 dropped 0.49%, zinc SZNcv1 rose 0.98%, lead SPBcv1 added 1.07% and tin SSNcv1 gained 1.81%.

($1 = 6.8030 Chinese yuan renminbi)