* April-June premiums mark the highest in 3 years
* Higher premiums reflect surging U.S. spot premiums
* Producers' initial offers were at $132-135/T
* Impact from new U.S. tariffs on aluminium unclear-buyer(Adds quotes and details)
By Yuka Obayashi
TOKYO, March 20 (Reuters) - Japanese aluminium buyers haveagreed to pay producers premiums for supplies of the metalduring the second quarter that are 25 percent higher than thefirst quarter, reflecting surging spot premiums in the UnitedStates, five sources directly involved in the quarterly pricingtalks said.
The two sides agreed to a premium <PREM-ALUM-JP> of $129 pertonne for metal to be shipped during the April to June quarter,up from $103 in the first quarter. The premium is the highest inthree years and marks the second consecutive quarterly rise.
Japan is Asia's biggest aluminium importer and the premiumsfor primary metal shipments it agrees to pay each quarter overthe London Metal Exchange (LME) cash price set thebenchmark for the region.
The latest negotiations began last month between Japanesebuyers and global producers, including Alcoa Corp, RioTinto and South32 Ltd, with initialoffers for premiums ranging between $132 and $135 a tonne.
The increase reflects a surge in U.S. spot premiums to thehighest in almost three years after U.S. President Donald Trumpflagged a 10 percent import duty, as buyers sought to securemetal before higher costs come into force.
Trump pressed ahead earlier this month with the tariffs butexempted Canada and Mexico and offered the possibility ofexcluding other allies, backtracking from an earlier"no-exceptions" stance.
U.S. spot premiums for Comex aluminium rose to about 19.2cents a pound ($423 a tonne) last week, the highestsince March 2015.
"All the contracts have been signed at $129 per tonne," asource at a Japanese aluminium fabricator said.
Three other buyer sources said they also struck their dealsat $129 per tonne while a source at a smelter said his companyagreed to pay $129 per tonne for its contracts.
The sources all spoke on the condition of anonymity due tothe sensitivity of the matter.
The new premium is lower than the U.S. spot level, but ishigher than current Japanese premiums in the low $120 a tonnerange, a source at a trading company said.
"It's still unclear how the U.S. new tariffs will affectglobal aluminium flow in the mid- to long-term as we don't knowwhich countries or products will be exempted or how soon and howmuch the U.S. smelters will resume operations," he added.
"I would be more interested in China's output after itswinter pollution controls," he added.
(Reporting by Yuka Obayashi; Editing by Christian Schmollinger)
