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April 13 (Reuters) - JP Morgan expects aluminium prices to average about $3,500 a metric ton over the second half of 2026, it said on Monday.

The bank also forecast a 1.9 million ton primary aluminium deficit in 2026, driven by a 2.4 million ton hit to Middle East supply. It highlighted that this would be the largest deficit since 2000 when accounting for overall market size.

JP Morgan noted a baseline view in which spot aluminium prices have upside potential to reach $4,000 a ton and above in the coming months, adding that it expects an average price of $3,800 a ton in the second quarter of this year as the scale of the supply disruption becomes increasingly evident in the physical market.

"Yet, we remain somewhat cautious of the longevity of aluminium prices trading at these levels given the demand risks from higher prices, supply unavailability and broader inflation trends that could become entrenched later in the year," the bank said in its note.

Aluminium prices jumped to their strongest in four years on Monday after Washington said it would impose a maritime blockade of Iran, reviving fears about weaker supply from top producers in the Gulf.

Benchmark three-month aluminium CMAL3 on the London Metal Exchange gained 1.7% to $3,558 a ton by 0930 GMT after touching $3,578 for its highest since March 31, 2022. MET/L

The Gulf region accounted for about 9% of global aluminium supply before this year's U.S.-Israeli attacks on Iran.