SIPTU says drivers are committed to finishing shifts before strike action begins on Thursday
Dublin Bus has said all services will terminate from 9pm tomorrow night as a first round of work stoppages get underway.
Trade unions SIPTU and the NBRU agreed a series of 48-hour stoppages across the month of September.
The stoppages will take place on September 8th, 9th, 15th, 16th, 23rd and 24th.
Workers at the state-owned company were balloted on industrial action after rejecting an 8.25% pay rise recommended by the Labour Court.
Union members had sought increases of up to 31%, to bring their pay in line with Luas drivers.
Talks aimed at averting strike action broke down last week.
Dublin Bus said that since the strike gets underway from 12am on Thursday morning, they have "no option but to terminate all routes at [9pm] on Wednesday night".
Final departures on all routes will be "up to and including" 9pm, to ensure "safe and secure" return of buses to depots, it said.
SIPTU hit out at the announcement this afternoon, saying drivers had intended to work tomorrow night before beginning industrial action.
"This is an unnecessary move which will just further inconvenience the travelling public," organiser Owen Reidy said.
"Dublin Bus drivers had committed to completing their shifts, even if this meant returning buses to their garages after the official start of strike action at 12.01 am on Thursday."
Mr Reidy added: "Since our members overwhelmingly voted in favour of industrial action last month, there has been no engagement with the Department of Transport or Dublin Bus management, apart from a one-hour meeting.
"At this meeting, management simply informed our union representatives that it was not willing to improve on the terms of a Labour Court recommendation which had already been categorically rejected by our members."
The NBRU, meanwhile, accused Dublin Bus of employing "inflammatory tactics".
"It seems that Dublin Bus are determined to unnecessarily ratchet up the pressure on its own customers to make alternative arrangements at short notice in order, as we see it, to paint its own staff in a bad light," the union said.
"It is nothing short of incredible that the company and its paymasters would resort to such chicanery."
Full details of how individual routes will be affected are available on the Dublin Bus website.
Ghostbus services will also be cancelled on Wednesday night.
No Dublin Bus routes, sightseeing tours or Airlink services will be operating on Thursday or Friday, while Nitelink services will also not operate on Friday/Saturday night (they will operate on Saturday/Sunday night).
The company said: "Dublin Bus has urged trade unions not to engage in this industrial action which will cause unnecessary inconvenience to customers. We will continue to make every endeavour to avoid any disruption to services and find a resolution to the matter."