Sales of existing homes in the United States plunged 8 percent in September, the biggest drop since 1999, driving down prices further, the National Association of Realtors reported Wednesday.

The plunge was steeper than the 4.5 percent decline expected by analysts and left existing home sales in September at a seasonally adjusted annual rate of 5.04 million units, the lowest level since 1999.

Existing home sales were down 10 percent in the Northeast region, 9.9 percent in the West, 7 percent in the Midwest and 6 percent in the South.

As sales plunged, prices also decreased. The median price of existing homes fell to 211,700 dollars in September, down 4.2 percent from a year ago.

The median price is the point at which half of existing homes are sold for more and half sold for less. September was the 13th month of the past 14 months when the year-on-year sales price decreased.

Meanwhile, the inventory of unsold homes rose to 4.4 million units in September. At the September sales pace, it would take 10.5 months to eliminate the overhang of unsold homes, a record length of time.

The huge inventories of unsold existing and new homes could put further downward pressure on prices, analysts say.

The once-sizzling U.S. housing market slid into the worst slump in 16 years, which has been a drag on overall economic growth. Many economists expect the Federal Reserve to cut interest rates further to prevent the economy from tumbling into a recession.