U.S. subprime mortgages have deteriorated a bit more rapidly than expected, said the International Monetary Fund on Tuesday, but adding that it is not likely to destabilize global financial stability.

The fallout in subprime segment "has so far been limited to a small number of lenders, but could yet spread to the structured credit markets," said the IMF in its Global Financial Stability Report.

The deterioration in the credit quality of subprime mortgages has, in turn, translated into wider spreads on securities collateralized by them, said the IMF.

U.S. residential mortgage-related securities represent one of the largest pools of fixed-income securities in the world, totaling around 5.8 trillion U.S. dollars, according to the IMF. Subprime mortgages account for around 14 percent of the 5.8 trillion dollars.

In December 2006, an announced bankruptcy of Ownit Mortgage Solutions, a small U.S. subprime mortgage lender, shocked the stock markets, said the IMF, adding such similar events would trigger volatility and disrupt broader asset markets.

However, the IMF concluded that major dislocation still appears to be "a low-probability event," and it also noted that the risks "would be heightened if many subprime credit events were to take place simultaneously."