The refuse contract for Brighton and Hove has not been signed nine days before new contractors are due to take over.
Serviceteam is set to take over the refuse collection and street cleaning contract on October 1, the day after thousands of visitors arrive in the city for the start of the Labour Party Conference.
Managers of the firm are still locked in negotiations with Brighton and Hove City Council.
A city council spokesman said: "Negotiations are ongoing and as yet we have not set a price on the contract."
He said the scope of the contract was also still under negotiation.
A spokesman for Serviceteam said he hoped the deal would be finalised on Thursday, three days before current operator Sita is set to leave.
Union representatives claimed they had not been told what would happen after September 30.
In a statement to The Argus, a spokesman for the GMB, which represents most of the workers, said: "The council is not even willing to talk to our union representatives who are trying to keep the workforce informed as to what will happen when Sita departs on September 30, removing all vehicles."
GMB organiser Gary Smith said: "We believe the talks over the future of the refuse and street cleaning contract are in crisis.
"The union believes negotiations between Serviceteam and Brighton and Hove City Council are deadlocked. The council is avoiding talking to us."
A spokesman for the refuse crews said: "Will we have vehicles, will we have pensions, will we have jobs? All we are asking for is for some straight talking from our elected representatives and council officers. We want the truth about who will take over and for this situation to be resolved. The residents and visitors to Brighton and Hove deserve it."
Sita, which has pulled out of its £6.7 million-a-year contract, confirmed it would be taking away its vehicles next Sunday, unless told otherwise.
The French-owned firm was sacked by the council following months of staff unrest, culminating in a four-day occupation of the main depot at Hollingdean in June.
Serviceteam, which operates similar services for 40 councils, has carried out detailed surveys of the city and the wage structure of the workforce.
A spokesman for the firm said: "We are hoping to soon sign the new agreement and are in discussions with the council."
The council has set a target price for the contract, which is higher than that paid to Sita.
A spokesman said: "We are not able to provide a running commentary on our negotiations over the new contract but we will give details after the outcome of negotiations. We are not able to confirm any figures as they are commercially sensitive."
The Argus last week revealed there were problems over pension arrangements and employment of agency workers by Serviceteam.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article