Thursday's strike will impact Metrolink, North Star, Go West, Waka Pacific, City LINK and Outer LINK bus services.

Bus drivers unhappy with working conditions are striking tomorrow, causing a disruption to services that could also inconvenience TPPA protesters.

Tramways and FIRST Unions are taking strike action between 9am and 2.30pm on Thursday to hold a meeting at Mt Eden War Memorial Hall for all drivers.

The hold on transport services coincides with the TPPA protest action in Auckland's CBD, where protesters will assemble at 12pm on Thursday to march down Queen St.

Starting on the Queen St side of Aotea Square, the demonstration will proceed down Queen St and finish with speeches and music at Britomart.

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Thousands were expected to participate in the march.

Tramways and FIRST Union are currently in wage negotiations with their employer NZ Bus, asking for more than the current offer of a 1.7 per cent increase.

Discussions had been ongoing for several months, with an agreement yet to be reached.

The two union groups last held a union meeting and put Auckland's bus services on hold in December 2015.

The strike will impact Metrolink, North Star, Go West, Waka Pacific, City LINK and Outer LINK bus services.

NZ Bus Chief Operating Officer Shane McMahon said the current offer could see real wages increase.

"We operate in a competitive landscape and we need to get the balance between increasing wages and remaining competitive".

McMahon said the strike was a "strange" move from the union.

"Most of our people are concerned about their jobs".

NZ Bus apologised for any inconvenience to customers during the strike.

Auckland Transport Bus Services Manager Brendon Main said Auckland Transport has been informed of the industrial action by NZ Bus and was trying to reduce the impact on passengers where possible.

"Auckland Transport is working with other bus operators to provide buses and drivers to maintain a skeleton service on key routes as we try to minimise disruptions to the travelling public."

Travellers should check with the Auckland Transport call centre or the Auckland Transport website before making travel plans to find out where services were available.