The Obama administration confirmed Friday that a piece of the 2010 health-care law aimed at helping small businesses provide insurance to their workers will be delayed by a year.

The office in charge of Medicaid and Medicare announced that it was on track for an Oct. 1 launch of the federal SHOP Exchange, an online marketplace where companies with fewer than 50 employees would be able to buy insurance for their workers and get a tax credit.

But employees will not be able to choose from a variety of plans, as was initially expected. They will be able to choose only one plan. The full range of options will not be available until 2015, the agency said.

The delay, proposed earlier this year, upset some business advocates and raised questions about whether the administration was behind on implementing the health-care law.

John Arensmeyer, head of the Small Business Majority, an advocacy group that supports the health law, said the news would likely discourage some businesses from offering insurance to their workers next year. While large businesses will be required to offer insurance beginning next year under the law, it will be optional for businesses with fewer than 50 employees.

But he said the delay will not be experienced in many states that took a leadership role in setting up their own health insurance exchanges.

“While we’re disappointed it’s not going to be there from day one, we’re pleased that feature will be there in most of the exchanges that are being run by the states, and they will be there for all the states beginning in 2015,” he said.