Westinghouse Electric Co, a unit of Japan's Toshiba Corp <6502.T>, said on Sunday it issued a lockout notice to 172 union members at its nuclear components manufacturing plant in Newington, New Hampshire, declaring that the sides had reached a stalemate in contract negotiations.
Westinghouse, which has been operating under bankruptcy protection, began formal negotiations with the International Brotherhood of Boilermakers, Iron Shipbuilders, Blacksmiths, Forgers and Helpers in April for a contract that expired almost a year earlier.
The Boilermakers and Westinghouse engaged in a mediation process that was not successful, and the union has refused to accept the company's last, best and final contract offer, the company said.
"As the Boilermakers were not willing to accept the offer, the company made the difficult decision to invoke a lockout," Michele DeWitt, Westinghouse interim senior vice president for nuclear fuel & components manufacturing, said in a statement.
The lockout was set to go into effect just before midnight on Sunday.
Union representatives did not immediately respond to email requests for comment.
(Reporting by Bill Berkrot; Editing by Sandra Maler and Andrew Hay)