June 18 (Reuters) - Goldman Sachs raised its average London Metal Exchange aluminium price forecasts for the third quarter of 2026 and full-year 2027 on Thursday, and said it expects gold prices to reach $4,900 an ounce by December.

It now sees the average third-quarter 2026 aluminium price at $3,300 a metric ton and average 2027 price at $2,950 per metric ton, up from previous views of $3,200 and $2,750 respectively.

It cited an assumption that Middle East production will face a slower recovery despite the potential reopening of the Strait of Hormuz after a deal to end the Iran war.

"The announced interim deal has reduced severe-disruption risk, but smelter output will likely recover more slowly than flows because damaged capacity must be repaired and restarted gradually," the bank said in a note.

Goldman sees the global aluminium market tightening more than previously expected, projecting a larger deficit in 2026 and a smaller surplus in 2027, as weaker Middle East output outweighs supply gains from Indonesia and China.

It forecast a 720,000 ton aluminium market deficit in 2026, and a 590,000 ton surplus in 2027, compared with previous expectations of a 570,000 ton deficit and a 1.3 million ton surplus respectively.

The bank added that risks around Middle East supply recovery are two-sided, noting that a slower restart of damaged Middle East capacity could keep the 2027 aluminium market surplus closer to 100,000 tons and prices around $3,250 per ton. However, faster Middle East recovery could lift the surplus toward 1.2 million tons and bring prices closer to $2,750 a ton.

LME aluminium CMAL3 was down 0.4% at $3,398.50 a ton as of 1615 GMT. MET/L

Goldman said in a separate note that it now expects gold prices to rise to $4,900 an ounce by December 2026.

Spot gold was trading over 1% lower at around $4,208.57 an ounce at 1939 GMT on Thursday. GOL/

It noted that continued central bank diversification remains the main structural driver of its constructive base case for gold prices.

"Our gold price views remain structurally constructive but tactically cautious with near-term downside risk and medium-term upside risk," the note said.

However, the bank said it sees lower demand for rate-sensitive gold exchange-traded funds.