LONDON—Anglo American PLC on Thursday said it has agreed to sell its niobium and phosphates businesses in Brazil to China Molybdenum Co. Ltd for $1.5 billion, marking another step in its quest to sell noncore assets and pare back debt against a backdrop of volatile commodities prices.

The sale is in line with Anglo’s plans, detailed in February, to sell more than half of its mines to focus on a smaller group of operations that can turn a profit even in a commodities downturn.

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