UPDATE 1-Japan Q4 aluminium premiums fall amid ample supplies and soft demand

* Oct-Dec premiums mark first quarterly drop in three

* Producers come down from initial offers of $105-115/T (Adds quotes and background)

TOKYO, Sept 27 (Reuters) - Premiums for aluminium shipments to Japan for October to December were set at $97 per tonne, down 10% from the previous quarter amid ample supplies in Asia and softening demand from the electronics and auto industries, three sources directly involved in the pricing talks said.

The figure is lower than the $108 per tonne paid in the July-September quarter and marks a first quarterly drop in three. It is also lower than the initial offers of $105-$115 made by producers.

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

“We had settled all of our October-December term contacts at $97 a tonne,” a source at a buyer said. “Producers came down from their initial offers due to weaker demand, especially in electronics and automobile segments.”

Japanese manufacturing activity shrank at the fastest pace in seven months in September, underscoring the broadening economic impact of the Sino-U.S. trade dispute and keeping policymakers under pressure to step up stimulus.

Abundant supplies in Asia also forced producers to compromise, the source said, citing higher supplies from Australia after U.S. pressure to reduce its aluminium export and increased output in India and the Middle East.

“All Q4 deals were done at $97 a tonne to reflect slow demand and lower spot premiums in Japan,” a source at a producer said, pointing to around $90 a tonne.

The sources declined to be named due to the sensitivity of the talks.

The latest quarterly pricing negotiations began last month between Japanese buyers and global producers, including Rio Tinto, and South32 Ltd.

Reporting by Yuka Obayashi; Editing by Jason Neely and Edmund Blair