ELIZABETH BECKER and EDMUND L. ANDREWS, The New York Times, report:

WASHINGTON, Jan. 7 With its rising budget deficit and ballooning trade imbalance, the United States is running up a foreign debt of such record-breaking proportions that it threatens the financial stability of the global economy, according to a report released Wednesday by the International Monetary Fund.

Prepared by a team of I.M.F. economists, the report sounded a loud alarm about the shaky fiscal foundation of the United States, questioning the wisdom of the Bush administration’s tax cuts and warning that large budget deficits pose “significant risks” not just for the United States but for the rest of the world.

The report warns that the United States’ net financial obligations to the rest of the world could be equal to 40 percent of its total economy within a few years “an unprecedented level of external debt for a large industrial country,” according to the fund, that could play havoc with the value of the dollar and international exchange rates.

The danger, according to the report, is that the United States’ voracious appetite for borrowing could push up global interest rates and thus slow global investment and economic growth.

“Higher borrowing costs abroad would mean that the adverse effects of U.S. fiscal deficits would spill over into global investment and output,” the report said.

White House officials dismissed the report as alarmist, saying that President Bush has already vowed to reduce the budget deficit by half over the next five years. The deficit reached $374 billion last year, a record in dollar terms but not as a share of the total economy, and it is expected to exceed $400 billion this year.

But many international economists said they were pleased that the report raised the issue.

“The I.M.F. is right,” said C. Fred Bergsten, director of the Institute for International Economics in Washington. “If those twin deficits of the federal budget and the trade deficit continue to grow you are increasing the risk of a day of reckoning when things can get pretty nasty.”

Administration officials have made it clear they are not alarmed about the United States’ burgeoning external debt or the declining value of the dollar, which has lost more than one-quarter of its value against the euro in the last 18 months and which hit new lows earlier this week.

“Without those tax cuts I do not believe the downturn would have been one of the shortest and shallowest in U.S. history,” said John B. Taylor, under secretary of the Treasury for international affairs.

Though the International Monetary Fund has criticized the United States on its budget and trade deficits repeatedly in the last few years, this report was unusually lengthy and pointed. And the I.M.F. went to lengths to publicize the report and seemed intent on getting American attention.

“I think it’s encouraging that these are issues that are now at play in the presidential campaign that’s just now getting under way,” said Charles Collyns, deputy director of the I.M.F.’s Western Hemisphere department. “We’re trying to contribute to persuade the climate of public opinion that this is an important issue that has to be dealt with, and political capital will need to be expended.”

The I.M.F. has often been accused of being an adjunct of the United States, its largest shareholder.

But in the report, fund economists warned that the long-term fiscal outlook was far grimmer, predicting that underfunding for Social Security and Medicare will lead to shortages as high as $47 trillion over the next 70 years or nearly 500 percent of the current gross domestic product in the coming decades.

Some outside economists remain sanguine, noting that the United States is hardly the only country to run big budget deficits and that the nation’s underlying economic conditions continue to be robust.

“Is the U.S. fiscal position unique? Probably not,” said Kermit L. Schoenholtz, chief economist at Citigroup Global Markets. Japan’s budget deficit is much higher than that of the United States, Mr. Schoenholtz said, and those of Germany and France are climbing rapidly.