* Graphic: Global asset performance tmsnrt.rs/2yaDPgn * Graphic: World FX rates tmsnrt.rs/2egbfVh LONDON, Aug 23 (Reuters) - European stocks opened higher and risk appetite in global markets increased on Monday, but worries about the COVID-19 Delta variant hampering economic growth persisted as investors weighed up the possible timeline for tapering monetary stimulus. After concerns about slower growth dragged stocks and oil prices lower last week, they picked up in Asian trading. The MSCI world equity index, which tracks shares in 50 countries, was up 0.4% at 0803 GMT, recovering after having its biggest weekly fall since June last week. Europe’s STOXX 600 was up 0.3%. Oil prices rose, breaking their seven-day losing streak. Brent crude was up 2.1% and U.S West Texas Intermediate crude was up 2%, after both marked their biggest week of losses in more than nine months last week as markets braced for weakened fuel demand due to a surge in virus infections. In currencies, the dollar index was at 92.264, down 0.2% on the day, compared to its nine-month high of 92.734 reached on Friday. “Following the corrections that we have seen over the last week, it’s really a bounceback,” said Marco Willner, head of investment strategy at NNIP. “People are looking at Jackson Hole, people are also looking at Delta variant, so the factors have not changed - it’s a technical bounceback.” The spread of the Delta variant has the potential to upset the timing of the U.S. Federal Reserve’s plans to taper its bond-buying programme. Dallas Federal Reserve President Robert Kaplan, among the U.S. central bank’s most forceful supporters for starting to reduce support for the economy, said on Friday he may need to adjust that view if the Delta variant of the coronavirus slows economic growth materially. Markets will be paying attention to Fed Chair Jerome Powell’s speech at Jackson Hole this week, although investors looking for clear indications about tapering may be disappointed. “One of the key questions will be when the tapering will start. I think it’s not a done deal that Powell will make any comments around this at all this week – he might wait til September, maybe even until November, make a major announcement around this one,” said NNIP’s Willner. Activity in Germany’s manufacturing and services sectors expanded in August, according to PMI surveys, although the pace of growth fell slightly. Germany’s benchmark 10-year yield was at -0.472% , while the U.S. 10-year yield was at 1.2717%, having lacked direction over the past week. Expectations that the U.S. Fed will ease its monetary stimulus sooner than the European Central Bank have helped the dollar strengthen against the euro in recent weeks, with the euro touching a nine-month low of $1.1664 on Friday. It was up 0.2% at $1.1724 at 0809 GMT on Monday. Elsewhere, bitcoin rose above $50,000 during Asian trading hours and was up 1.7% on the day at around $50,154. The cryptocurrency reached an all-time high of 64,895.22 in April, dropped sharply in May, and has been gradually recovering since mid-July. For Reuters Live Markets blog on European and UK stock markets, please click on: Reporting by Elizabeth Howcroft Editing by Nick Tattersall Our Standards: The Thomson Reuters Trust Principles.