Workers at the Coles distribution centre at Somerton in Melbourne's north have rejected the latest offer from management.
Site manager Toll Holdings has offered workers a 3.5 per cent pay increase and extra payments for regular shift workers.
But the National Union of Workers says staff are demanding shift penalty rates and want to accrue rostered days off.
Hundreds of Coles workers walked off the job at Somerton more than two weeks ago, stopping trucks from entering or leaving the warehouse.
The union's Tim Kennedy says workers are maintaining the picket, but the dispute could be resolved soon.
"We believe based on the proposal we put back to the company today we are quite close," Mr Kennedy said.
"We believe if the company focuses on the economic imperatives that we've addressed and deals with these things in good faith, we believe there is an agreement there," he said.
Mr Kennedy says he hopes the dispute will be resolved soon but workers at the picket are prepared to wait it out.
"This is not a holiday, this is a very hard struggle," he said.
"These workers are normal Australian citizens, good working people, they are fighting a very powerful force," he said.
A spokesman for Toll has criticised the union for taking a vote, saying negotiations are continuing.
The dispute is due back before Fair Work Australia on Monday.