Tobacco companies have introduced almost no cigarettes or smokeless tobacco products in the U.S. in more than 18 months because the federal government has prevented them from doing so.

An Associated Press review has found that the Food and Drug Administration has not ruled on nearly 3,500 product applications. About 90 percent have lingered for more than a year, much longer than the expected 90-day review process.

FDA officials say the applications have languished because of “significant deficiencies” and because the agency is taking extra care in reviewing products that pose public health risks.

Industry executives say cigarettes haven’t changed in any meaningful way and the delays don’t make sense. At the same time, tobacco watchdogs say there are signs cigarette makers are skirting the process with some new products.