JEFFERSON CITY -- Missouri will be unable to implement a key provision of federal health care law, Gov. Jay Nixon announced Thursday.

It will be up to the federal government to establish a health insurance exchange in Missouri, Nixon said. The exchange is designed to be an online marketplace where individuals and small businesses can compare and buy private insurance plans.

As part of the Affordable Care Act, states face a Nov. 16 deadline to notify the federal government if they want to run their own insurance exchange, which must be open for business by 2014. If they do not, the federal government will step in and set up an exchange.

“I think it’s a duty best handled by the state,” Nixon said, later adding: “But a state-based option is not on the table at this time.”

This week, voters approved a ballot measure prohibiting the governor from establishing an exchange without the involvement of the General Assembly. Nixon said because of the constraints of that ballot measure, along with reluctance by Republican legislative leaders, the only option left is to tell the federal government Missouri will be unable to proceed with a state-based exchange.

A bill creating the “Show-Me Health Insurance Exchange” cleared the Missouri House last year with unanimous support. The measure died in the state Senate, however, after several Senators expressed concerns. It was never brought up during the most recent legislative session, and House leadership expressed little enthusiasm for the idea following the 2012 elections.