Robert Rubin is approaching his 59th birthday but looks years younger. He is handsome enough to be a Hollywood star but instead has the less glamorous, but infinitely more powerful, job of US Treasury Secretary. This week he is locked in a vital struggle with Republicans in Congress over President Clinton's plan for a balanced budget by 2002. But the deal includes tax cuts on the capital gains of the rich and tax credits for the low paid with children who are just below the income tax level, but are liable for payroll taxes for social security benefits.

Mr Clinton and Mr Rubin oppose indexing the capital gains tax reduction. The Republicans oppose a tax credit for low-paid workers saying that this is really an extension of welfare and the president has been boasting that he has "ended welfare as we know it".

Robert Rubin came from a Cabinet meeting where these mega-issues were being thrashed out to talk on the record over lunch with foreign correspondents at the USA Today headquarters with its panoramic view across the river to Washington's power centres.

Mr Rubin refuses any dessert and also refuses to get dragged into European squabbling over the euro. "I don't want to get into that. I just focus on our policies and what I can do. I have no great wisdom beyond that," the former Wall Street, whiz-kid with Harvard, Yale and London School of Economics degrees, said modestly.

The Irish Times tried to prod him on the euro as a possible rival to the dollar as a reserve currency. Yes, the US has been looking at the implications of this but personally Mr Rubin found that the best assessment was a recent Bank of International Settlements study.

The message Mr Rubin took from it was: "If we (in the US) keep our house in order, we don't have to worry about the euro becoming a second reserve currency. The dollar will remain a reserve currency. From our point of view it is better to have a Europe that is growing and prosperous so I do not have any concern about the euro as a reserve currency." The dollar will not be "used as a trade weapon" he promised.

What concerns Mr Rubin more at the moment is the battle ahead with Congress for President Clinton to get fast-track authority to negotiate an extension of the North American Free Trade Agreement (NAFTA) to Chile and other Latin American countries. Fast-track authority means that when the deal is signed, the Senate can only approve or reject it but not amend it under pressure from vested interests.

The big labour unions are still unhappy with NAFTA's effect on US jobs and will extract a big price for supporting fast-track. Democratic minority House leader, Dick Gephardt, and presidential contender, is also opposing it so the Republicans will have to be wooed hard in the coming months.

Republicans trust Mr Rubin with his Wall Street, background. He worked in New York for the Goldman Sachs investment banking firm for 26 years and in virtually every financial market from bonds to commodities. But he is also a lifelong Democrat.

Former Labour Secretary, Robert Reich, who has gone back to academia after a frustrating time in Washington has written about his clashes with Mr Rubin when Mr Reich used to flail at the big corporations for their ruthless downsizing to increase profits.

Mr Reich was regularly hauled in by Mr Rubin and his predecessor Lloyd Bentsen for lectures. Mr Reich comments in his memoir, Locked In Cabinet, "When Rubin runs out of arguments, he uses his `I was there and you weren't' trump card." He also says that Mr Rubin who punctuated his clashes with Mr Reich with "I profoundly disagree", is "the only person in the Administration who can profoundly disagree without raising his voice".

Mr Rubin is modest about the much-envied success of the US economy under his tenure as steady growth is accompanied by a two-thirds cut in the budget deficit, 12 million new jobs, the lowest unemployment in 24 years and inflation under 3 per cent.

At the Denver G-7 Summit, or Summit of the Eight if you count Russia, some of the US senior officials could not help gloating over how President Clinton's record compared with the struggling economies of the Europeans, especially France, Germany and Italy.

President Clinton has praised Mr Rubin's concern, while in New York, for the underprivileged saying that throughout his life he (Rubin) has "manifested concern for the welfare of all Americans and a special concern for the welfare of the inner-city poor".

Now, of course, under President Clinton, the Roosevelt-era federal safety net for the poor has been abolished and the states have been ordered to get those on welfare back to work with the help of block grants from Washington.

Mr Rubin is not too perturbed by this. "Welfare reform is conceptually right - creating incentives to move from welfare to work."

Talking about moving, Mr Rubin has denied that he is moving from the Cabinet back to real work on Wall Street.