"As of right now US economic growth is at zero," he said, adding the longer it stayed this way the greater the risk of a deep recession.

Wall Street giants Goldman Sachs and Merrill Lynch have both forecast that the US economy will contract in 2008.

The US Federal Reserve has said 2008 growth will be between 1.3% and 2%.

The forecast, made last week, was half a percent lower than the Fed's previous estimation.

The gloomy outlook was blamed on falling house prices, reduced bank lending, turmoil in the financial markets and higher oil prices.

Mr Greenspan also predicted that booming oil prices, which reached a record of more than $101 last week would keep rising and that the US housing market would see more misery before the tide turned.

But he expresses deep disappointment with Bush. "My biggest frustration remained the president's unwillingness to wield his veto against out-of-control spending," Greenspan writes. "Not exercising the veto power became a hallmark of the Bush presidency. . . . To my mind, Bush's collaborate-don't-confront approach was a major mistake."

Greenspan accuses the Republicans who presided over the party's majority in the House until last year of being too eager to tolerate excessive federal spending in exchange for political opportunity. The Republicans, he says, deserved to lose control of the Senate and House in last year's elections. "The Republicans in Congress lost their way," Greenspan writes. "They swapped principle for power. They ended up with neither."

He singles out J. Dennis Hastert, the Illinois Republican who was House speaker until January, and Tom DeLay, the Texan who was majority leader until he resigned after being indicted for violating campaign finance laws in his home state.

"House Speaker Hastert and House majority leader Tom DeLay seemed readily inclined to loosen the federal purse strings any time it might help add a few more seats to the Republican majority," he writes.

He adds three pages later: "I don't think the Democrats won. It was the Republicans who lost. The Democrats came to power in the Congress because they were the only party left standing."

However, he calls Clinton a "risk taker" who had shown a "preference for dealing in facts," and presents Clinton and himself almost as soul mates. "Here was a fellow information hound. . . . We both read books and were curious and thoughtful about the world. . . . I never ceased to be surprised by his fascination with economic detail: the effect of Canadian lumber on housing prices and inflation. . . . He had an eye for the big picture too."

During Clinton's first weeks as president, Greenspan went to the Oval Office and explained the danger of not confronting the federal deficit. Unless the deficits were cut, there could be "a financial crisis," Greenspan told the president. "The hard truth was that Reagan had borrowed from Clinton, and Clinton was having to pay it back. I was impressed that he did not seem to be trying to fudge reality to the extent politicians ordinarily do. He was forcing himself to live in the real world."

Dealing with a budget surplus in his second term, Clinton proposed devoting the extra money to "save Social Security first." Greenspan writes, "I played no role in finding the answer, but I had to admire the one Clinton and his policymakers came up with."

Greenspan interviewed Clinton for the book and clearly admires him. "President Clinton's old-fashioned attitude toward debt might have had a more lasting effect on the nation's priorities. Instead, his influence was diluted by the uproar about Monica Lewinsky." When he first heard and read details of the Clinton-Lewinsky encounters, Greenspan writes, "I was incredulous. 'There is no way these stories could be correct,' I told my friends. 'No way.' " Later, when it was verified, Greenspan says, "I wondered how the president could take such a risk. It seemed so alien to the Bill Clinton I knew, and made me feel disappointed and sad."