Prime Minister Boris Johnson is preparing to call an election, British media reported on Monday, on the eve of an historic showdown with Parliament over Brexit.

Johnson's promise to take the country out of the European Union on Oct. 31 with or without a deal to smooth the divorce between the world's fifth-largest economy and its biggest trading partner has propelled the United Kingdom toward a constitutional crisis and a battle with the 27 other members of the bloc.

An alliance of opposition lawmakers are plotting with rebels in Johnson's Conservative Party to take control of Parliament and tie the government's hands with legislation that would block a no-deal exit, fearing leaving without a deal will be ruinous.