Gold held the biggest gain in six months after the Treasury Department made a surprise move to rein in long-term borrowing costs. Bullion was trading above US$4,500 an ounce, after surging more than 4 per cent the day before. The Treasury unexpectedly announced it is ramping up buybacks of long-dated government debt, signalling it wants to lower borrowing costs after yields hit multi-decade highs. The department said it’s “increasing, by at least double, the size of liquidity support buyback operations” for securities dated from the 10-year to the 30-year sector. Hours later, it disclosed that total US public debt had surpassed US$40 trillion (S$50.85 trillion) for the first time. It has now surged by a third in less than five years.The move signals greater official support for the Treasury market and potentially easier financial conditions, which lower the opportunity cost of holding gold. However, further gains in the yellow metal may be tempered by energy-led inflation pressure. Oil held a gain, as prospects for a peace deal between the US and Iran over the Strait of Hormuz remained dim and a spat between the United Arab Emirates and Iran added to tensions in the Middle East.More Federal Reserve officials supported raising US interest rates in July than the three who formally dissented, while others indicated they could back a hike if inflation fails to improve, according to minutes of the central bank’s July meeting released on Aug 19. Higher rates are typically negative for bullion, which carries no interest. Spot gold rose 0.1 per cent to US$4,520.05 an ounce at 7.21am in Singapore. Silver advanced 0.1 per cent to US$67.01 an ounce. Platinum and palladium also edged higher. The Bloomberg Dollar Spot Index, a gauge of the US currency, was little changed after ending the previous session down 0.8 per cent. BLOOMBERG