FILE PHOTO: Employees work at a copper smelter in Yantai, Shandong province, China April 26, 2023. REUTERS/Siyi Liu/File Photo

By Polina Devitt

LONDON (Reuters) -Metals analysts are cutting their estimates of global copper supplies for this year and next after an accident at the giant Grasberg mine dramatically tightened the outlook for the market.

Copper prices hit 15-month highs of $10,485 a metric ton last week after Freeport-McMoRan declared force majeure at its Grasberg mine and cut sales forecast from the Indonesian unit for this year and 2026.

Freeport's Grasberg operation located in Indonesia suspended operations on September 8 after a deadly mud slide.

The world's second-largest copper mine behind Chile's Escondida faces a lengthy damage assessment process and a clear-up while the search for missing workers continues.

"The scale of this disruption is very big," said Albert Mackenzie, a copper analyst at Benchmark Mineral Intelligence.

Benchmark's analysis suggests the disruption will amount to 591,000 tons of lost copper output between September 2025 and the end of 2026.

This amounts to 2.6% of the 2024 global mine production estimated at around 23 million tons by analysts.

Supply losses from Grasberg mean the global copper market is facing a significantly wider deficit of around 400,000 tons in 2025, according to Benchmark Minerals.

The disruption has shifted Goldman Sachs' 2025 copper market balance from a projected surplus of 105,000 tons to a deficit of 55,500 tons. It expects a small surplus in 2026.

With the losses in Grasberg's September-December production, the copper market faces the largest deficit since 2004, Societe Generale said on Monday.

The suspension at Grasberg follows other large disruptions this year including Kamoa-Kakula in the Democratic Republic of Congo and El Teniente mine in Chile.

This year's mine supply was already expected to come in below every forecast over the past 15 years and this is now exacerbated by unexpected supply disruptions, Bank of America analyst Michael Widmer said in a note.

BofA raised its estimate of the 2026 copper market deficit to 350,000 tons from a previous 162,000 tons and upgraded its 2026 and 2027 copper price forecast by 11% and 12.5% to $11,313 a ton and $13,500 respectively.

Copper's record high was in May 2024, when it hit $11,104.50 a ton.

(Reporting by Polina Devitt; editing by Tomasz Janowski)