By John S. McClenahen Persistent economic weakness in the U.S. is causing the 15-nation European Union (EU) to revise its economic forecasts for 2001 and 2002. Average GDP growth for the group will be an inflation-adjusted 2.8% this year and 2.9% next, 0.3% and 0.1% lower than previous forecasts, estimates the Brussels-based European Commission. Inflation is expected to average 2.1% this year and 1.8% in 2002. Among the 15 nations, Ireland, again, is expected to be the fastest growing economy, with a 7.5% advance this year and 7.1% growth in 2002. Denmark is expected to turn in the weakest performance -- 2.1% growth in 2001 and 2.4% in 2002. In addition to Ireland, six other EU countries --Belgium, Finland, Greece, Luxembourg, the Netherlands, and Spain -- are forecast to post at least 3% growth in both 2001 and 2002.