LONDON (Reuters) - The U.S. dollar fell broadly against its peers on Wednesday, snapping a three-day rising streak, as signs of progress in tackling the COVID-19 pandemic boosted risk appetite with the Chinese yuan climbing to its highest level in 2-1/2 years. With U.S. coronavirus cases crossing the 15 million mark on Tuesday, regulators moved a step closer to approving a COVID-19 vaccine while Britain started inoculating people on Tuesday. Riskier currencies including the Australian dollar led gains against the struggling greenback in early London trading with U.S. stimulus plans boosting stock markets to record highs. Investors are also tracking negotiations over U.S. coronavirus aid, with the Trump administration proposing a $916 billion package on Tuesday after congressional Democrats rejected a slimmer plan. Elsa Lignos, global head of FX strategy at RBC Capital Markets, wrote in a daily note that markets seen comfortable with the idea “that eventually something will get done.” Against a basket of its rivals, the greenback fell 0.2% to 90.70, snapping a three-day rising streak. It weakened 0.2% against the euro to $1.2126 and is tracking toward an annual loss of 8% against the common currency, its largest since 2017, as economic activity data suggests Europe outperforming the United States in recent weeks. The dollar dropped to 6.5198 yuan in onshore trading, its lowest since June 2018, putting the yuan up by more than 10% from its May lows, boosted by the softer dollar and steady inflows into Chinese stocks and bonds. The British currency was volatile in early trading, up 0.4% at $1.3410 before a Wednesday dinner between British Prime Minister Boris Johnson and European Commission President Ursula von der Leyen in Brussels that is seen as a last-ditch attempt to salvage a Brexit trade deal. Rumblings in the money markets grew with swap markets indicating a growing demand for dollars heading into the year-end. Three-month euro cross-currency basis swap spreads widened to minus 32 bps, well below a March peak of nearly minus 90 bps.