(Adds context in paragraph 9, details of asset sale in...

(Adds context in paragraph 9, details of asset sale in paragraph 10, updates shares)

SailingStone Capital Partners, a shareholder in First Quantum Minerals FM.TO , said on Monday it had told the Canadian miner about historic "missed opportunities" in the management of its balance sheet and a range of options to bring down its leverage.

"We have expressed our view to the company on the range of options that are (there) and some of the missed opportunities around how they managed the balance sheet and their hedge book and what the priorities are ...," MacKenzie Davis, a managing partner at the investment firm, told Reuters in an interview.

First Quantum is dealing with the fallout from the sudden closure of its flagship Panama copper mine, which accounted for about 40% of its revenue. It has lost more than half its market value since public protests over that mine started in the Central American nation last October.

It announced a series of measures last week to bring down costs, and said it was exploring several options to raise funds, including the sale of smaller mines and bringing in strategic investors for its large mines.

SailingStone Capital Partners owns 0.2% of First Quantum shares, according to a regulatory filing.

First Quantum did not offer an immediate comment. Davis said First Quantum's guidance on debt management from last week was not specific, but added that SailingStone is confident the mining firm is reviewing all of its options. He said First Quantum has the ability to navigate through some tight windows in the debt market.

First Quantum has a debt repayment worth $1.05 billion due in April 2025.

When asked if SailingStone as a shareholder would support asset sales, Davis said: "Tell me the price and I will give you an answer, tell me what assets are being sold and the price and we will think about it."

Last week Reuters reported that the company was exploring a rights issue - an invitation to existing shareholders to purchase additional new shares in the company - and hired BMO Capital Markets to sell some of its smaller mines such as Las Cruces in Spain.

First Quantum has lost C$11 billion ($8.2 billion) of its market value since last November due to its problems in Panama. As of Monday, it had net debt of C$7.5 billion and a market value of C$8.70 billion.

Ratings firm Fitch warned last December that if the mine in Panama were permanently shut, First Quantum's net debt leverage ratio in 2024 would increase to more than five times its earnings before interest, tax, depreciation and amortization, which could result in a covenant breach.

First Quantum shares were trading down 0.6% on the Toronto Stock Exchange on Tuesday. ($1 = 1.3454 Canadian dollars)