Proposals for a "Greater Birmingham" which would replace the West Midlands as an official English region are to be examined by the city council's chief executive.
Lin Homer has joined a high-powered commission looking at ways of reforming local government by focusing on the major cities.
It also includes the chief executives of Sheffield and Nottingham councils, and the leaders of Manchester, Liverpool, Gateshead and Kent councils.
Called the City Regions Commission, it was formed after Government plans to introduce regional assemblies across England were thrown into disarray when voters in the North-east rejected the scheme in a referendum.
Civic leaders believe major changes to local government may still be needed.
They will look at the possibility of "super-sizing" cities. In Birmingham's case, this would mean bringing together Birmingham and surrounding authorities, including Solihull and much of the Black Country.
The commission will also examine whether cities such as Birmingham should have mayors.
Any recommendations made by such a high-powered group representing many major cities would be hard for Ministers to ignore.
Creating a Greater Birmingham would mean the end of proposals for an elected democratic assembly covering the whole West Midlands region. Ministers have already privately confirmed they are willing to consider creating a separate region bringing together Herefordshire and Worcestershire, which are currently part of the West Midlands, and neighbouring Gloucestershire, currently classed as part of the South-west region.
The official regions are used by the Government to allocate hundreds of millions of pounds of funding.
But critics claim cities such as Birmingham have little in common with rural shires such as Herefordshire and it makes no sense to lump them together for administrative purposes.
Devolution in Scotland, Wales and London has increased the pressure on other regions of Britain to set up structures for promoting themselves nationally and in Europe.
The commission has been organised by the New Local Government Network, an independent think-tank.
It will hold seminars, question witnesses, and commission research, and present its conclusions in the summer.
Witnesses giving evidence will include Ed Balls, former chief economic adviser to the Chancellor, and experts on local government from universities.
Warren Hatter, head of NLGN's research unit, said: "This is a chance to get behind the rhetoric of "city regions" to see whether they are a realistic option and, if they are, in what form they can be made to work."