PORTLAND, Maine (AP) — The telephone service provider for Maine, New Hampshire and Vermont declared an impasse after four months of labor negotiations, while more than 1,700 workers for the company were advised by union officials Thursday to be on “standby” for a possible strike or lockout.

The International Brotherhood of Electrical Workers and Communication Workers of America accused FairPoint Communications of violating federal law and asked the National Labor Relations Board to reinstate the contract that expired on Aug. 2.