WASHINGTON (AP) -- The U.S. Chamber of Commerce is launching ads in Senate races in Florida, Missouri, Hawaii and Ohio and in 17 House contests.

Officials with the chamber say the ads will begin airing on Wednesday and Thursday and will be in rotation for 10 days to two weeks.

The national political director for the chamber, Rob Engstrom, says the purpose of the ads six months before the election is to help protect business-friendly incumbents while challenging lawmakers the group says have voted against business interests.

The ads in House races will air in New York, Illinois, Michigan, Minnesota, Ohio, Rhode Island, Florida and Georgia.

The chamber declines to say how much it's spending. Ad buys earlier this year in eight Senate races and 12 House races was estimated at $10 million.