He said the action could include anything from working to rule to a full withdrawal of labour, and no dates had been specified.
Mr Hughes said drivers were disappointed the bus company was refusing to resume pay talks until the end of January, and he feared that would result in a protracted dispute.
NZ Bus executive Tonia Haskell said the company was pleased to advised that all its Auckland services had resumed after the meeting.
"Bargaining with the First and Tramways unions will resume in January 2016 -- we are looking forward to a constructive conversation that results in positive outcomes for all parties," she said.
"Meri Kirihimete and enjoy the festive season."
First Union is also in pay talks with four smaller bus companies, all preparing to try to outbid one other in new route tendering rounds with Auckland Transport.
Mr Hughes said another company from outside Auckland, which was non-unionised, was also waiting for an opening in the city and he called on the council transport agency to put a higher rating on quality of services in its evaluation of bids.
A strike notice again Birkenhead Transport was withdrawn yesterday, after the company backed down on an alleged attempt to reduce overtime pay, but other talks such as with Ritchies Transport and Howick and Eastern remain up in the air.
An Auckland Transport spokesman said his council organisation did not intend commenting on the bus company pay talks.