FRANKFURT (MktNews) - The euro's decline against the dollar over the past several weeks is "difficult to explain" in the face of the sharp U.S. economic slowdown, European Central Bank (ECB) Chief Economist Otmar Issing said Thursday. But he suggested that part of the explanation could be that global investors may believe that the U.S. slowdown could be a short-lived affair. "That could be an explanation but only part of it. I don't know for sure," Issing told an audience of bankers at an event sponsored by Dresdner Bank. Issing declined to comment on specific exchange rate levels. "Short-term foreign exchange developments are difficult to explain," Issing said. According to him, the euro's past weakness as reflected by extensive investment flows out of Europe, could not be explained by a lack of confidence in the euro's internal stability. Rather, "many factors contributed to not making the eurozone investors' highest area of priority," Issing said. Issing argued that external developments, especially in the United States, had been the main determinant of the euro's exchange rate. Even though the European economy saw "two good" years in 1999 and 2000 this performance "paled" in comparison to that of the United States.