WASHINGTON (AFP) - A key index tracking the US economy rose slightly in May after being flat a month earlier but recovery from recession is expected to slow, the Conference Board said Thursday. The business research firms forward-looking leading economic index (LEI) rose 0.4 percent after Aprils 0.1 percent decline was revised to no change. The financial components made the largest positive contributions to the index, more than offsetting the substantial negative contributions from stock prices and building permits, the board said. The LEI has been on an uptrend for more than a year but its six-month growth rate up to May has continued to moderate, the board said. The index points to continued, though slower, US growth for the rest of this year, said Bart van Ark, chief economist of The Conference Board. He said public debt and deficits weighed heavily on growth prospects in the United States as well as Europe. We project a serious slowdown in European growth in 2011, which could further weaken the US outlook. The boards coincident index, a measure of current economic activity, rose 0.4 percent in May, following the same increase in April and a 0.3 percent gain in March. The US economy plunged into its worst recession in decades in December 2007 amid a financial crisis triggered by a home mortgage meltdown. The economy began to grow in the middle of last year after about a year of contraction but is still mired in nearly double-digit unemployment, with more than eight million jobs lost since the start of the recession.