The creation of a three-way "super force" for the north-east of England has been put into doubt after two chief constables proposed to go it alone.
The Home Office has backed a preferred plan to merge the Northumbria, Durham and Cleveland forces.
But Cleveland is resisting the proposal in favour of a smaller merger with Durham to create a Tees Valley force.
Now the chief constables of Northumbria and Durham say they may go it alone "for the benefit of policing."
The decision casts doubt over the future of Cleveland Police - one of the smallest areas in the country.
A statement issued on behalf of the Northumbria and Durham forces said: "The Northumbria and Durham forces and their police authorities are aware Cleveland Police Authority remains opposed to the option of a single regional force.
"Under these circumstances, and in order to make progress for the benefit of policing services in the area, Northumbria and Durham's chief constables and their police authorities have indicated to the Home Secretary that they would be willing to explore a merger of Northumbria and Durham forces, but only as part of a staged process leading to a larger regional force in the future."
Northumbria's Chief Constable Mike Craik said: "We believe a single strategic force is the right way to develop a police service able to cope with current and future demands."
Durham's chief constable, Jon Stoddart, added: "Durham and Northumbria have a long tradition of working together and both forces enjoy enviable records for policing neighbourhoods and reducing crime.
"Amalgamation is the only way to increase the level of all services we deliver to the people of the North East."
The chairman of the Cleveland Police Authority, Councillor Dave McLuckie said: "Today's developments show that, in reality, the creation of a single merged force for the North East is a dead duck."
He claimed the development was a vindication for the position the Cleveland Authority and force had taken during the debate.