* Dollar index hits 31-month trough, kiwi hits 2.5-year high * Aussie and euro mark three-month peaks vs greenback * Graphic: World FX rates in 2020 tmsnrt.rs/2RBWI5E By Tom Westbrook SYDNEY, Nov 30 (Reuters) - The dollar touched a more than two-year low on Monday and is set to log its largest monthly fall since July as a combination of vaccine optimism and bets on more monetary easing in the United States drove investors out of the world"s reserve currency. Against a basket of currencies, the greenback slipped 0.1% to 91.707, its lowest since April 2018. The risk-sensitive New Zealand dollar hit a two-and-a-half year high and is headed for its best monthly percentage gain in seven years. "The themes remain familiar: broad dollar weakness amid improving risk appetite," ANZ Bank analysts said in a note. "This sentiment is likely to continue into December and the (U.S. Federal Reserve) meeting, at which some further action is likely, given the near-term virus risks in the United States." The euro and Australian dollar each rose slightly to hit three-month peaks, though moves were small as world stocks took a breather at the end of the biggest calendar month rally on record. The Aussie is up more than 5% for the month, the kiwi 6.3% and the euro 2.8%. Sterling stood at $1.3325 and is up nearly 3% on the dollar this month as investors wager a Brexit deal will be brokered even as the deadline for talks loomed ever larger. The dollar index has dropped about 2.5% in November as promising trial results for major vaccine candidates excited investors about an eventual end to the coronavirus pandemic. It is nearly 11% below a March peak of 102.990. Nervousness about a wave of new infections across Europe and the United States and fresh lockdowns have provided some support to safe-haven currencies and a slight brake on the dropping dollar. However, as the drawn-out U.S. election has distracted lawmakers from passing any sort of fiscal spending package, investors have begun to expect that the Fed will step in, probably with more bond buying, when it next meets in December. Testimony from Fed chair Jerome Powell before Congress on Tuesday and Wednesday, as well as U.S. labour market data this week will be closely watched for clues as to the central bank"s thinking and the broad shape of the economy recovery. The Japanese yen was 0.3% firmer at 103.87 per dollar on Monday and has gained a little over half a percent through November as the death toll from the pandemic climbed towards 1.5 million people. "The dollar is gently drifting to the lows of the year as investors re-allocate portfolios to recovery trades in the rest of the world," ING strategists Chris Turner and Francesco Pesole said in a note to clients. "While more lockdown restrictions may stand to curb U.S. equity markets, the prospect of the Fed being prepared to add more liquidity should limit any dollar upside. And given that the dollar index has fallen in seven of the last ten Decembers, we do favour gentle dollar downside into the end of the year." November also marks a sixth consecutive monthly gain for the Chinese yuan, which has soared some 9% from a low in May. That equals a similar run of monthly gains six years ago, but it is far larger in magnitude as global capital flows in to ride China"s remarkable coronavirus recovery. Month-end dollar demand weighed on the Chinese currency on Monday, offsetting another month of strong economic data, and the yuan fell 0.2% to 6.5851 per dollar. The greenback was broadly steady elsewhere, although bitcoin advanced 2% to $18,557. It is up 34% this month, its largest monthly gain since April. Later in the day, investors are awaiting European inflation data and, at 1030 GMT, a speech from European Central Bank President Christine Lagarde. ======================================================== Currency bid prices at 4:16PM in Sydney (0516 GMT) Description RIC Last U.S. Close Pct Change YTD Pct High Bid Low Bid Previous Change Session Euro/Dollar $1.1970 $1.1965 +0.05% +0.00% +1.1974 +1.1959 Dollar/Yen 103.8650 104.0500 -0.17% +0.00% +104.1550 +103.8500 Euro/Yen 124.33 124.50 -0.14% +0.00% +124.6600 +124.3100 Dollar/Swiss 0.9033 0.9045 -0.12% +0.00% +0.9046 +0.9034 Sterling/Dollar 1.3338 1.3318 +0.16% +0.00% +1.3343 +1.3324 Dollar/Canadian 1.2993 1.2985 +0.08% +0.00% +1.2995 +1.2978 Aussie/Dollar 0.7386 0.7384 +0.03% +0.00% +0.7407 +0.7384 NZ 0.7028 0.7035 -0.09% +0.00% +0.7045 +0.7025 Dollar/Dollar All spots Tokyo spots Europe spots Volatilities Tokyo Forex market info from BOJ