Firefighters would be forced to breach safety rules to save lives if plans to cut fire engines resurface, a union has warned.
Proposals to axe one of Wrexham's engines were scrapped by North Wales Fire and Rescue Authority in March, until after the May elections.
The new authority is yet to rule out the cut as it sets its budget plan for the next three years.
Deputy Chief Fire Officer Dawn Docx said any cuts would be a "last resort".
While there are no proposals to cut front-line services, the Fire Brigades Union (FBU) fears the engine will face the axe again as the authority tries to deal with budget pressures.
Cerith Griffiths, of the FBU, said the cut would force firefighters to breach safety protocols to save lives.
Under the service's safety rules, which set out how many crews should attend a particular incident - known as a predetermined response, two fire engines are needed in the event of a house fire.
Mr Griffiths said if the second engine was cut, firefighters would be forced to choose whether to wait crucial minutes or enter a burning building without back-up, putting their own lives at risk.
"When you look at Grenfell in London, firefighters broke all kinds of protocols there, if we haven't got that second engine we shouldn't be going into that property," he said.
"We have seen firefighters will push the boundaries to save someone.
"If you are waiting half an hour for the second engine, that's a long time in a situation where every second counts, that's a long time if you are trapped.
"It is putting lives in danger."
Proposals to axe one of Wrexham's two fire engines and 24 firefighter posts, to plug a £900,000 funding gap by 2020, were withdrawn by the fire authority in March following public opposition.
The station is the only one in north Wales with three fire engines - two full-time and one part-time engine.
The new authority is now preparing to set its own budget plans and is canvassing public opinion ahead of publishing its draft financial strategy in November.
Ms Docx said no proposals had yet been put forward, but the service was looking at ways to make savings without affecting front-line jobs.
A fire engine may have to be axed from a station, meaning crews would have to wait "slightly longer" for back-up, she said.
"There would have to be a judgement call - do we wait for the second pump or do we go in," Ms Doxc said.
"I certainly wouldn't want to leave you with the impression this is something that senior fire officers want," she said.
"If we are in that position where we can't close the gap with the budget this is the option that the authority could consider"."