LONDON -- Deputy Prime Minister John Prescott issued a blunt warning Thursday to local authorities in the British firefighters' dispute, saying there would be no blank cheque to end the pay row.

Prescott's warning -- aimed at making the government's position "absolutely clear" -- came on the eve of fresh talks to resolve an eight-day strike that is set to end today.

In a letter to local government association chairman Jeremy Beecham, whose group is negotiating with the Fire Brigades Union (FBU), Prescott reiterated government fears that a big pay increase would harm the British economy.

"Any pay award not affordable within existing public expenditure provision must be paid for by modernization," or changes in firefighters' working practices, Prescott said. "These negotiations are between you and the fire brigades union," he added. "But there are serious implications for government, for public sector pay policy as a whole, and the broader public interest."

The FBU -- which plans a major protest today to mark the end of the strike -- had agreed to a 16 percent increase just hours before the strike began last week, a significant backdown from its initial 40 percent demand.

But the proposal was shot down by Prescott on grounds that the real cost had not been fully calculated -- thus triggering the most serious labor dispute since Prime Minister Tony Blair took office.

Some 250 protesting firefighters greeted Blair with a deafening wail of sirens as he arrived Thursday to deliver a speech on Europe in the southern Welsh city of Cardiff.

"We have come from all over South Wales and will be making our presence felt throughout Mr. Blair's stay in Cardiff," said Clive Protheroe, a firefighter based in Cardiff.

Seven people have died in house fires since the walkout began, leaving military personnel and cold war-era fire trucks known as "Green Goddesses" to respond to the most serious emergency calls.

If no agreement is forthcoming, the FBU is threatening more eight-day strikes from December 16, AFP reported.