"We welcome the launch of the euro, an historic step that 11 nations in Europe have taken toward a more complete economic and monetary union," US president Bill Clinton said in a statement. "A successful economic union that contributes to a dynamic Europe is clearly in our long-term interests."

"A strong and stable Europe, with open markets and robust growth, is good for America and for the world," he added.

Clinton's endorsement of the euro, which today made a strong debut on the world's foreign exchange markets, followed a series of more guarded comments by other top US officials.

Treasury secretary Robert Rubin earlier repeated his long-standing mantra that what is good for Europe will be good for the United States -- adding, that euro's launch underscored the need for sound economic policies at home.

"It will be a currency like all other currencies," he told reporters. "As we've said many times, if it's good for Europe then that's good for the United States. A strong Europe is good for the United States."

The 11 countries that adopted the single currency -- Austria, Belgium, Finland, France, Germany, Ireland, Italy, Luxembourg, the Netherlands, Portugal and Spain -- almost match the United States' economic might.

Their total annual output of about $6.5 trillion compares to almost $8 trillion in the United States. And according to European estimates, the euro zone will form the world's greatest trading power, with 1997 exports 25 per cent larger than those of United States and twice those of Japan.

The euro zone's weight in the world economy has prompted some to fear a shift of investor money out of the US dollar into the euro. That would make it harder for the United States to attract the capital it needs to finance its rising trade deficit, eventually pushing up interest rates and putting a damper on growth.

"Some more or less equitable sharing of international roles between the two (currencies) is quite likely," US economist Fred Bergsten told Reuters in an interview.

"(The euro will) move up alongside the dollar in what will amount to a bipolar international monetary regime, replacing the dollar dominance of the past 60 or 70 years. I think it's matter of a few years," he added.