The ruling executive of the Fire Brigades Union announced the walkout on March 20 after rejecting a revised 16% three-year offer over "unacceptable" strings tied to the deal.
The move in effect invited a government bid to outlaw the stoppage on public safety grounds under 1992 Tory legislation, with the 19,000 troops who answered emergency calls during four previous strikes now either stood down or posted to the Gulf.
Downing Street has received legal advice from the attorney general and is expected to make a final decision shortly if possible peace moves fail to avert the threatened walkout.
Andy Gilchrist, the FBU's general secretary, admitted that the industrial action would be "extremely disappointing to the nation" but blamed fire authority employers and claimed the latest package on the table would lead to a "free-for-all" of cuts and job losses.
"It is our wish to negotiate, even compromise, at this late stage but the fire service employers have failed to meet our concerns," Mr Gilchrist said.
The deputy prime minister, John Prescott, is expected to review his options in the next few days ahead of the union's decision to hold a conference of 500 activists in Brighton next Wednesday on the eve of what would be the fifth stoppage in the six-month dispute.
Last night Mr Prescott said it was "very regrettable" that the union had decided to call a fresh strike.
"It would have been better if they had waited for their conference next week before deciding to reject the offer," he said. "It is something the membership of the FBU should have a say on."
FBU leaders were incensed when the employers handed a four-page document explaining last week's offer to the press ahead of a meeting with senior union officials.
Although the draft deal presented by fire chiefs was substantially the same as an outline agreement already turned down, the apparent breach of protocol underlined the worsening relations between the two sides.
John Ransford, a director of the Local Government Association who handed out copies on the steps of a central London hotel, insisted it would be accepted by any other group of public service workers.
He said any decision to seek an injunction to avert industrial action "was a matter for the government" rather than the fire authorities.
After two hours of talks had failed to find a meeting of minds, Mr Ransford admitted: "It's certainly not a way to run a fire service and we want to avoid strikes. We want to get people working normally, working constructively."
Re-mobilising the 19,000 troops and more than 800 vintage green goddess tenders to respond to 999 calls next Thursday would be a difficult task for armed forces already overstretched by the deploy ment to the Middle East.
Government and union lawyers have privately indicated that an injunction would not be automatically granted, although fears of a terrorist outrage would strengthen the hand of ministers.
Firefighters would also risk a media and public backlash if they go on strike when soldiers, sailors and airmen were risking their lives in the Gulf.
Mr Gilchrist is aware of the public relations pitfalls and, pressed on the potential conflict of interests, said last night: "The first point is war is not inevitable and the FBU represents the nation's firefighters and control staff."
Conditions attached to the 16% three-year offer have emerged as a bigger stumbling block than the money, because the 58 UK fire brigades would be given the power to impose radical reforms to staffing and operational duties without agreement.
The employers claimed that conceding the right to agreement rather than consultation would grant the union a veto and the draft document even states that disputes would only be referred to a special arbitration panel if both sides consented.
Firefighters yesterday lobbied MPs in the House of Commons and a Hull union mem ber claimed Mr Prescott had admitted he would not endorse the draft deal if he were still a shop steward.
The FBU said the threat to jobs had been underlined by moves in Strathclyde to reduce the number of crew members on appliances from five to four.
John McGhee, a union national officer, said: "It is as if the employers are trying to write a script to force firefighters on strike again."
