U.S. Homebuilders sentiment the housing market is becoming less optimistic as a tax credit for first-time homebuyers that boosted home sales in the past month is nearing its end.

The National Association of Home Builders said Monday this month's housing market index fell by one point to 18, the first drop since June when the reading fell to 15.

The builders’ expectations for the next six month are also diminishing as buyers have softened since September. This come about as the outlook dimmed as the federal tax credit for first time home buyers is about to expire and homebuyers must complete their transactions by November 30.

"It would be virtually impossible at this point to complete a new home sale in time to take advantage of that buyer incentive," said David Crowe, the NAHB's chief economist.

The NAHB is lobbying for support a 12-month extension of the program. "That would amount to a very effective stimulus to housing demand and a needed boost to the overall economy," Crowe said.

Despite rising unemployment, new home sales have improved five months in a row.

The index reading for current sales conditions fell one point to 17. Traffic by prospective buyers dipped three points to 14. The sales expectations index over the next six months dropped two points to 27.

The report covers 493 residential developers nationwide in a survey, monitoring builders' confidence about market conditions. Index reading higher than 50 indicates builders’ positive sentiment about the market.

The last time it was above 50 was in April 2006.