Volatile metals and oil prices, uncertainties over BHP's financial policy and liabilities tied Samarco are key to the credit assessor's outlook, he said. "Our balance sheet strength has been maintained with both cash flow and gearing metrics within our target ranges, liquidity of $16 billion and a long-dated debt maturity profile," BHP said in an e-mailed statement. The producer seeks to ensure its strategy supports a solid 'A' credit rating, it said in an annual report published Wednesday.