(Adds more details of investment, background on Peru copper)...

(Adds more details of investment, background on Peru copper)

LIMA, Sept 25 (Reuters) - Peru's largest copper mine, Antamina, plans to start work next year on a delayed project to extend the lifespan of its site until 2036, the firm's president said, while awaiting official approval of the environmental license.

Victor Gobitz, president of Antamina, controlled by Glencore GLEN.L , BHP (BHP) , Teck TECKb.TO and Mitsubishi 8058.T , told Reuters the bulk of an estimated $2 billion investment will be spent in 2025.

Antamina had hoped to win environmental approval for the so-called "Antamina Replenishment" project in the first half of this year, but the country's mines and energy ministry said it would approve this by the end of 2023.

"With the environmental license we will immediately seek the construction license, which has short time frames, and in a few months we will be ready to start carrying out the investment in 2024," Gobitz said in a telephone interview.

The project aims to extend the exploitation of the mine, which produced 467,905 metric tons of copper last year and is located in the Andean region of Ancash, for eight more years.

Antamina has not ruled out requesting a further extension of its mine's lifespan. The site also produces silver and zinc.

Peru's government has forecast that mining investment will fall this year and next year nationwide amid political uncertainty and a shrinking economy, but still counts $53 billion-worth in mining projects in its development pipeline.

Gobitz said that Peru, the world's second largest copper producer, must boost investment in the sector ahead of an expected increase in global demand for the metal - used in electrical generators and wiring - over the coming years.

"China, the big buyer of copper, is currently suffering from a real estate crisis, but after this there is a good outlook in the medium- and long-term," said Gobitz. "We should bear this in mind in order to be ready."