International Monetary Fund chief Christine Lagarde Wednesday gave an upbeat appraisal of the world economy, but said the US Federal Reserve's tapering could bring "rough waters" ahead.Speaking at the National Press Club, Lagarde's projections echoed the rosier outlook earlier in the day by the World Bank, but she gave greater emphasis to the looming hurdles. "This crisis still lingers. Yet, optimism is in the air: the deep freeze is behind, and the horizon is brighter," Lagarde said. In its Global Economic Prospects report earlier in the day, the World Bank said growth was picking up in developing countries and high-income economies appeared "to be finally turning the corner."But with the US central bank starting to downsize its "massive monetary stimulus," there could be headwinds from rising global interest rates and potential volatility in capital flows, the bank warned.For the US, Lagarde warned against "premature" withdrawal of the stimulus and urged the country to return to an orderly budget process after it once again barely avoided tumbling over the fiscal cliff in October 2013.The World Bank projected global growth in 2014 at 3.2 per cent, up from the 2.4 per cent in 2013, and by 2016 projected it to reach 3.5 per cent. Gross domestic product (GDP) in the wealthier countries was expected to climb from an average of 1.3 per cent in 2013 to 2.4 per cent in 2016 .In developing and emerging economies, growth is expected to jump from 4.8 per cent in 2013 to 5.7 per cent in 2016 . The eurozone is projected to grow 1.1 per cent this year, 1.4 per cent in 2015 and 1.5 per cent in 2016, putting behind it two years of contraction.US GDP, which has expanded for 10 quarters, is projected to grow 2.8 per cent in 2014 and 3 per cent by 2016, the World Bank said.