Labourers work at a steel factory in Dalian, Liaoning province July 13, 2012. China's economy grew 7.6 percent in the second quarter of 2012 from a year earlier, its slowest pace in three years. (China Daily/Reuters)

An economic slowdown in China and other major developing countries has pulled one of the few remaining props from the world economy, which is already threatened by the financial crisis in Europe and a sluggish U.S. growth.

Strong growth among developing countries, particularly the so-called BRIC nations — Brazil, Russia, India and China — as well as Mexico and South Africa, had been a bright spot in an otherwise tepid world recovery.

No longer.

Growth is now slowing among those nations as well. And for a variety of reasons, they may not be able to respond with the same intensity as they did after the U.S. financial collapse in 2008, when they pumped hundreds of billions of dollars into government projects and other measures to stimulate their economies.

Those efforts kept their own economies on track and helped ease the recession in the developed world by boosting the demand for exports from countries such as the United States. Sales to China from the United States, for example, jumped more than 80 percent between the first months of 2009 and the first months of 2012.

That rapid run-up is losing steam, prompting the International Monetary Fund on Monday to trim its forecasts for global growth and warn that worse problems may be in the offing.

This could also spell a further drag on the U.S. economy, which is struggling with an 8.5 percent unemployment rate.

“World leaders are casting around for some source of growth outside their own borders, and it is increasingly hard to find,” said John G. Murphy, vice president for international affairs at the U.S. Chamber of Commerce. “The past two years have seen rapid export growth [in the United States]. There is a growing concern that is behind us.”

The chief global worry remains Europe, where agency officials acknowledged that the emergency steps taken so far have failed to remove the financial pressures on the major economies of Italy and Spain and ensure that their governments will be able to continue raising money from investors. In some of their bluntest language yet, top IMF analysts said the European Central Bank may need to resume buying government bonds. Otherwise, Italy and Spain could be forced to seek massive international bailouts, which could paralyze world financial markets.

IMF officials also warned that the U.S. economy has its own threats. In particular, the United States is facing the danger later this year that political gridlock may prevent the government from raising its borrowing limit, which could lead to national default, and from heading off the enormous spending cuts due to take effect next year. The latter could could drive the United States back into recession.

The IMF’s warning about worsening conditions in the developing world was evidence that the global economic recovery remains vulnerable despite repeated rounds of government stimulus and years of low interest rates.

A slowdown in the developing world was not totally unexpected. Developing countries depend heavily on exports to the richer developed world, where economic conditions have remained difficult.

Neither is the slowdown wholly unwelcome. China’s 10 percent annual rate of growth was not considered sustainable, and the country in recent months had been trying to slow lending and rein in its rapidly appreciating real estate prices. Strong growth in Brazil attracted such a flood of international investment that officials there worried about suddenly skyrocketing currency values and looked for ways to temper the influx of money.

But the overall confluence of events has analysts worried. Like the United States and Europe — beset by high public debt and annual deficits — each of the big developing nations faces its own constraints, leaving less room to maneuver if conditions get worse.

India, for example, is saddled with high government deficits, while the money that flooded quickly into Brazil is now starting to leave: Stock values and the currency have been falling in value this year. In China, lending expanded so fast in recent years that the current economic slowdown could raise separate concerns about the impact that bad loans or falling asset prices would have on banks’ financial health.

China already has begun loosening credit and lowering interest rates, and officials said they hoped to boost investment as well. Growth there is still expected to hit 8 percent for the year.

However the IMF cautioned that another burst of credit in China “would heighten asset quality concerns and potentially undermine GDP growth and financial stability in the years ahead.”Brazil is also taking steps to bolster growth, while Russia remains buoyed by recent oil receipts.

Those steps and others may yet take hold. But with Europe and the United States struggling, the world’s previous star performers are now at risk as well.

“If and when a large downside shock ultimately materializes . . . combined vulnerabilities could quickly come to the fore, putting financial stability to a serious test,” the agency concluded.