Talks between the T&G union and Heathrow-based caterers Gate Gourmet have been put on hold until Wednesday after breaking up amid acrimony.
The issue of how many people can picket has been to court
T&G chief negotiator Brendan Gold initially accused the firm of leaving talks about the sacking of 670 workers.
But the company denied that, saying it was "cautiously optimistic" of a deal and would return to talks on Wednesday.
It said a move to place the company, which supplies British Airways, into administration would be put on hold.
Gate Gourmet has refused to take back all the workers it dismissed two weeks ago.
After 18 hours of talks over two days, the union said a sticking point remained over the reinstatement of sacked workers.
A new catering deal with British Airways was struck earlier on Tuesday, but it is dependent on labour issues being resolved.
Gate's new contract was reported to involve a two-year extension to its contract to supply food to the airline at a better price until 2010.
Gate Gourmet had warned it faced going into administration in the UK unless it got a better contract from BA and set an original deadline of 1700 BST on Tuesday for reaching an improved deal.
The TUC helped to bring the two sides together. As talks were adjourned there on Tuesday evening, Mr Gold accused managers of walking out.
"I'm very disappointed and disgusted at the way things have been concluded this evening," he said.
"The main issue is the reinstatement of all our members."
However, the union later told the BBC it would rejoin talks on Wednesday.
But Gate chairman David Siegel said he was optimistic an agreement over sacked staff could be reached and negotiations had been "productive".
He insisted the company would not reinstate all the workers, despite it being one of the key T&G demands.
"We have some real hard-liners who instigated the action," he said, adding that Gate did not want to "sell out" the 1,400 employees at Heathrow.
Mr Siegel praised the TUC general secretary Brendan Barber.
"We made substantial progress to finding a solution, unfortunately we didn't get there yet," he said.
The dispute broke out 12 days ago when Gate Gourmet sacked 670 staff after they illegally walked out in protest at its restructuring plans.
A day later BA ground staff at Heathrow walked out in sympathy, forcing the airline to shut down operations at the airport - resulting in the loss of £30m as it cancelled 700 flights.
Gate Gourmet director Andy Cook has said a new deal with BA had been vital to the firm's survival, as it is losing £25m a year.