Gold held near $4,500 an ounce, posting its biggest gain in six months after the US Treasury Department announced a surprise buyback operation aimed at reducing long-term borrowing costs. The move sent Treasury yields lower, weakening the dollar and boosting demand for non-yielding bullion.

The Treasury's decision to repurchase longer-dated securities caught markets off guard, signaling heightened concern over rising yields and their impact on financial conditions. Yields on 10-year and 30-year Treasuries dropped sharply following the announcement, removing a key headwind for gold.

Traders said the buyback underscores the Treasury's willingness to act as a backstop for the bond market, a development that could keep gold prices elevated near record highs. The metal's advance also reflects persistent central bank buying and geopolitical uncertainty.

Analysts note that if the Treasury continues such operations, it may cap yield upside and provide a sustained tailwind for precious metals. However, any hawkish shift in Federal Reserve policy could reverse the recent momentum.