* All three major U.S. stock averages higher * Dollar sinks to lowest since April 2018 * Stimulus check negotiations continue in Washington * Graphic: 2020 asset performance tmsnrt.rs/2yaDPgn * Graphic: World FX rates in 2020 tmsnrt.rs/2egbfVh (Updates to U.S. market open, changes dateline to NEW YORK (was LONDON), changes byline) NEW YORK, Dec 30 (Reuters) - Wall Street advanced and the dollar dipped to its lowest in more than two years on Wednesday, the penultimate trading day in an extraordinary year of pandemic, recession and recovery. All three major U.S. stock indexes were up in a broad rally, as impending stimulus and the ongoing rollout of COVID-19 vaccines fed optimism over economic recovery in 2021. “I would caution against reading too much into trading action this week because it’s a shortened week and volumes are typically down, so there tends to be more volatility,” said Chuck Carlson, chief executive officer at Horizon Investment Services in Hammond, Indiana. “The dollar is a continuation of what we’ve seen in the last few months,” Carlson added. “This is partly in anticipation that since Europe had a deeper decline, its rebound will have more of a snap-back.” U.S. Senate Majority Leader Mitch McConnell introduced a bill late Tuesday that combines beefier $2,000 direct fiscal aid payments to Americans with provisions involving social media company protections and election security. Britain approved a coronavirus vaccine developed by Oxford University and AstraZeneca in the latest development in the rapid progression, testing, approval and deployment of drugs to battle the disease. The Dow Jones Industrial Average rose 165.7 points, or 0.55%, to 30,501.37, the S&P 500 gained 13.87 points, or 0.37%, to 3,740.91 and the Nasdaq Composite added 34.01 points, or 0.26%, to 12,884.23. European stocks reversed gains and headed slightly lower as investors took profits in the wake of strong gains. The pan-European STOXX 600 index lost 0.13% and MSCI’s gauge of stocks across the globe gained 0.49%. Emerging market stocks rose 1.58%. MSCI’s broadest index of Asia-Pacific shares outside Japan closed 1.67% higher, while Japan’s Nikkei lost 0.45%. U.S. Treasury yields were essentially flat on Wednesday morning in thin trading as investors bet that Republicans were unlikely to approve the passage of proposed $2000 stimulus checks. Benchmark 10-year notes last fell 1/32 in price to yield 0.9364%, from 0.935% late on Tuesday. The 30-year bond last fell 4/32 in price to yield 1.679%, from 1.674% late on Tuesday. The dollar fell the lowest since April 2018 against a basket of world currencies as investors bet on more fiscal support and positioned for year-end in light trading volume. The dollar index fell 0.41%, with the euro up 0.36% to $1.2291. The Japanese yen strengthened 0.42% versus the greenback at 103.15 per dollar, while Sterling was last trading at $1.3608, up 0.80% on the day. Crude oil prices gained ground on the back of the weaker dollar and a dip in U.S. inventories. U.S. crude rose 1.27% to $48.61 per barrel and Brent was last at $51.33, up 0.47% on the day. Gold gained ground as the safe-haven metal countered a dip in the greenback. Spot gold added 0.3% to $1,884.41 an ounce.