* U.S. dollar off two-month highs reached on Friday * Australia dollar at lowest since December 2020 * Drop in iron ore prices hurts Aussie * Graphic: World FX rates tmsnrt.rs/2RBWI5E TOKYO/SYDNEY, June 21 (Reuters) - The dollar index, which rose after the Fed’s surprise hawkish tilt last week, gave up some of its gains on Monday, while the Australian currency stumbled on lower prices of the country’s top export, iron ore. The dollar index, which tracks the greenback against six major currencies, slipped to 92.286 from a high of 92.405 reached on Friday, a level not seen since April 13. It jumped 1.9% last week - the most rise since March 2020 - as the U.S. Federal Reserve signalled a sooner-than-expected end to its ultra-easy monetary policy, triggering a collapse in U.S. shares and prompting analysts to revise their forecasts for stock and currency performance. The Fed’s policy stance has become a tailwind for the dollar, accounting for a challenging backdrop for risk assets, Westpac analysts said. While the index has the scope to test highs reached in March after its recent impulsive gains, “there’s not enough juice for a sustained medium-term breakout beyond that”, they added. Analysts at Goldman Sachs agreed the dollar’s gains may not be sustained, noting other central banks will need to consider policy normalisation too as their economies recover from the depressed levels brought on by the pandemic. Benchmark 10-year U.S. Treasury yields fell to the lowest since early March at 1.4110% during Asian trading, while those on 30-year bonds slid as low as 1.9990% for the first time in more than four months. The yield curve, or the spread between two- and 30-year yields, was the flattest since early February. As the Fed’s hawkish stance dulled investor risk appetite, the safe-haven Japanese yen rose to a one-week high against the dollar. It was last up 0.3% at 109.80 per dollar. In other currencies, the Aussie fell to $0.7474, a level not seen since Dec. 21, 2020, driven by a 5% drop in iron ore prices as a seasonal slowdown in construction activity in top steel producer and consumer China hit sentiment. The euro was barely changed at $1.1859, having hit a 2-1/2-month low of $1.1847 on Friday. The British pound hit a two-month low of $1.3790 on Monday. In cryptocurrencies, bitcoin fell 4% to $34,016, while ether changed hands at $2,077.58. Reporting by Hideyuki Sano in Tokyo and Swati Pandey in Sydney; editing by Richard Pullin and Himani Sarkar Our Standards: The Thomson Reuters Trust Principles.