TOKYO (Reuters) - Rio Tinto (>> Rio Tinto Limited) (>> Rio Tinto plc) has offered Japanese buyers aluminium at a record premium of $420 (253 pounds) per tonne for October-December primary metal shipments, up 3-5 percent from the previous quarter, four sources involved in pricing talks said on Tuesday.

Japan is Asia's biggest importer of the metal and the premiums for primary metal shipments it agrees to pay each quarter over the London Metal Exchange (LME) cash price set the benchmark for the region.

Rio Tinto's offer was below the $460 offer made by Russia's United Company Rusal Plc (>> United Company Rusal Plc) last week.

Rio Tinto could not be reached by phone to comment on its offer.

For the July-September quarter, Japanese aluminium buyers mostly agreed to pay record high premiums of $400-$408 per tonne , over LME prices, up 8-12 percent from the quarter before that.

(Reporting by Yuka Obayashi; Editing by Tom Hogue)

Stocks treated in this article : United Company Rusal Plc, Rio Tinto Limited, Rio Tinto plc