'The key issue is liquidity. Investors rush into the US dollar, euro and other currencies rather than into gold and silver because they want cash at hand and the ability to meet payment obligations,' Thorsten Polleit says ISTANBUL   Gold prices have struggled to extend gains despite escalating geopolitical tensions and sharp volatility in oil markets, as investors prioritize liquidity and high-yielding assets while awaiting clearer signals on US monetary policy. Precious metals have traded near