By Louise Radnofsky Small employers in 18 states will offer only one health plan to workers when the Affordable Care Act's small-business exchanges open this fall, federal officials said Tuesday.The 2010 law called for new online insurance marketplaces, which were supposed to open last year, for small businesses to pick group plans to cover workers. But those exchanges were delayed a year, and federal officials say they will lack some functions when they open in November.The federal health law also called for employees at small businesses to be able to choose from a range of plans on the exchanges. Federal regulators said they were allowing states to restrict employees to the plan designated by their employer to avoid the risk of premium increases.Some state insurance commissioners had worried that letting employees choose from a range of plans could lead to some products ending up with a small number of workers who then incur big medical bills. Commissioners feared insurers would raise prices to guard against that prospect.Regulators said Tuesday they approved 18 states' requests to limit the choice to one employer-designated plan. The regulators said state insurance commissioners had shown that allowing employees to choose from a range of plans could cause health insurers to charge more. That was based largely on the assumption that a small number of unhealthier employees might be drawn to particular plans.The Centers for Medicare and Medicaid Services, which is implementing the health law, said it was allowing states to limit workers' choices for one year as a transition.The federal government is going to operate the small-business exchanges this year on behalf of 32 states that didn't want to set up their own, including the 18 states that will offer only one health plan later this year. The launch of small-business exchanges initially was delayed because of the federal government's technical problems implementing it.The Obama administration has told insurers the small-business exchanges are set to launch on Nov. 15, with pilot testing in October, but that they initially will be missing some functions for technical reasons, including the option for employers to contribute different amounts for part- and full-time employees.The 18 states getting a year's delay on offering employees multiple plans are: Alabama, Alaska, Arizona, Delaware, Illinois, Kansas, Louisiana, Maine, Michigan, Montana, New Hampshire, New Jersey, North Carolina, Oklahoma, Pennsylvania, South Carolina, South Dakota and West Virginia.The 14 other states where the federal government is running the exchanges, and where small-business employees can choose from several plans, are: Arkansas, Florida, Georgia, Indiana, Iowa, Missouri, Nebraska, North Dakota, Ohio, Tennessee, Texas, Virginia, Wisconsin and Wyoming.House Small Business Committee Chairman Sam Graves (R., Mo.), who has criticized the implementation of the health law, said the latest change would add to employers' difficulties."This pattern of continued delays and confusion is especially disappointing to me and the small-business community as many firms grapple with increased health costs," he said. John Arensmeyer, head of the Small Business Majority, which represents about 8,000 businesses supportive of the law, said he was "extremely disappointed" by the decision, and questioned the administration's legal basis for it. "Just imagine trying to run a small company and keep up with all of the changes and delays regarding this law," added. Write to Louise Radnofsky at louise.radnofsky@wsj.com