* Euro STOXX 600 down 1.1% * Sterling down 0.5% * Brexit uncertainties, U.S. stimulus timing dent sentiment * Oil extends gains as Brent rises above $50 * 2020 asset performance tmsnrt.rs/2yaDPgn LONDON/TOKYO, Dec 11 (Reuters) - World shares slipped on Friday as tricky Brexit negotiations and uncertainty over U.S. stimulus talks capped riskier bets even though COVID-19 vaccines made progress, pushing sterling down and keeping the dollar weak. European equities fell, with the broad Euro STOXX 600 down 1.1% and indexes in Paris and London losing 1.2% and 1% respectively. The MSCI world equity index, which tracks shares in 50 countries, fell into the red. U.S. stocks were mixed on Thursday as near-term U.S. fiscal stimulus appeared unlikely. Democrat House Speaker Nancy Pelosi suggested wrangling over a spending package and coronavirus aid could drag on through Christmas. Brexit also vexed investors after British Prime Minister Boris Johnson said on Thursday there was “a strong possibility” Britain and the European Union would fail to strike a trade deal. Britain and the EU have set a deadline of Sunday to find an agreement, before Britain’s exit from the bloc on Jan. 1. The odds of a disorderly Brexit rose to 61% on Friday from 53% a day before, according to the Smarkets exchange. Sterling lost 0.5%, and was set to end five straight weeks of gains as currency traders weighed an expected hit to the British economy should the sides fail to agree a deal. “Investors are right to be worried,” said Olivier Marciot, a portfolio manager at Unigestion. “If there is no deal, there will be implications. There could be some sort of correction.” U.S. futures gauges fell 0.2%. Still, investors had bet on stronger economic growth next year as more countries prepare for vaccinations, helping MSCI’s ex-Japan Asia-Pacific index edge up 0.2% and head for its sixth straight week of gains. U.S. authorities voted overwhelmingly to endorse emergency use of Pfizer’s coronavirus vaccine while doses of a COVID-19 vaccine made by China’s Sinovac Biotech SVA.O are rolling off a Brazilian production line. UPBEAT IPOs, DOWNBEAT JOBS Demand for recent U.S. initial public offerings also suggested investors were generally upbeat on equities, even as job data pointed to weakness in the world’s biggest economy. Shares of Airbnb Inc more than doubled in their stock market debut on Thursday, valuing the home rental firm at just over $100 billion in the biggest U.S. initial public offering of 2020. DoorDash Inc stocks doubled in their first day of trading. At the same time, the number of Americans filing claims for unemployment benefits grew more than expected last week as mounting COVID-19 infections led to more business restrictions. The data “raises the prospect that the labour market progress seen in recent months is slowing significantly,” Deutsche Bank analysts wrote. In the currency markets, the British pound traded at $1.3228 , with its 1.5% loss so far this week versus the dollar setting it on course for a first weekly loss since late October. Emerging-market currencies were poised for a sixth week of gains, thanks in part to the dollar’s recent weakness. The dollar was up 0.2% against a basket of six major currencies , near lows not seen since spring 2018. The euro held not far from two-and-a-half-year highs of $1.2140 after the European Central Bank delivered a fresh stimulus package that was broadly in line with market expectations on Thursday. Oil prices climbed further, with Brent hitting levels not seen since early March, as coronavirus vaccination rollouts fuelled hopes that crude demand would pick up in 2021. Brent crude rose 0.1% to $50.36 per barrel.