The Euro opened the week down against the dollar on Monday, amid concerns over the U.S. currency's rapid decline in recent weeks, the Associated Press reported. The 15-nation euro bought US$1.5777 in early Monday trading, down from the US$1.5835 it bought in New York late Friday. Britain's pound dipped to US$1.9712, compared with US$1.9724 in New York. The dollar slumped to 100.63 Japanese yen, down from 101.01 in late Friday trading.