LONDON — Since Britain’s vote in June to quit the European Union, its government has promised repeatedly to make a success of withdrawal, known as Brexit.

More than two months later, however, it still cannot say how.

On Wednesday, Prime Minister Theresa May called cabinet ministers to a brainstorming session about the withdrawal, pledging to examine “the next steps” for Britain and to identify “opportunities that are now open to us as we forge a new role” in the world.

However, in ministerial offices, where turf wars have rapidly broken out, advocates of the withdrawal have discovered that four decades of European integration have left Britain so deeply embedded in the 28-nation bloc that there is no easy escape route.

British officials currently have neither the expertise nor the staff for the tortuous exit negotiations, which are likely to last at least three years and possibly much longer. Some analysts have even said they might take a decade.