Andy Gilchrist, the secretary general of the Fire Brigades Union, said his members would go on strike from 9pm on January 21 until the following evening despite a day of talks.
He said the union was still being required to commit itself "unreservedly" to recommendations in the Bain review into the fire services.
"This approach is totally wrong, dangerous and unjustified," the union leader said, echoing words used by the prime minister to describe the FBU's campaign of industrial action.
The union has asked the employers to remove its insistence that it had to agree to the Bain recommendations.
The two sides met for five and a half hours at the London headquarters of the conciliation service Acas, far longer than had been expected.
But they emerged to give separate briefings and different views on the outcome of the meeting.
Officials from fire authorities said they believed "there was a reasonable possibility" that a 24-hour walkout next Tuesday would be suspended.
Charles Nolda, secretary of the employers organisation, said: "We have had quite a useful discussion. It is the start of a long and difficult process."
He said both sides had spelled out their positions in the long running dispute over the union's claim for a 40% pay rise to give firefighters a basic salary of £30,000.
He made it clear that the employers were sticking to recommendations in the Bain review but he said there would be room for negotiation.
"There is a reasonable possibility that next week's strike will be suspended," he said.
But the FBU said the strike was set to go ahead.
Employers will hold further talks over the next few days and the union's executive will meet on Thursday before a meeting of FBU delegates on Friday when a fresh campaign of strikes is expected to be announced.
Further talks could be held next Monday, just hours before the nationwide walkout is due to start.
Two 48-hour strikes from January 28 and February 1 could follow.
