TOKYO, March 12 (Reuters) – Some Japanese aluminium buyers have agreed to pay some global producers a premium of $129 per tonne for shipments in the April to June quarter, reflecting soaring U.S. spot premiums, two sources directly involved in the pricing talks said on Monday. The new premium is 25 percent higher than the $103 per tonne premiums in the current quarter and is the highest in three years. It also marks the second quarterly increase in a row. Japan is Asia’s biggest importer of aluminium 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.