U.K. Prime Minister Boris Johnson formed a war Cabinet of six senior ministers to plan for exiting the European Union by Oct. 31, as a key adviser said leaving without a deal had become a very real prospect, the Sunday Times reported.

Johnson's most senior aide, Dominic Cummings, a key leader in the 2016 Brexit campaign, called advisers to the prime minister's residence Friday night and told them Brexit will happen "by any means necessary," the Times said. Cummings said Johnson is prepared to suspend Parliament or hold an election to thwart those who may seek to block a no-deal Brexit.

Michael Gove, a Johnson ally writing in the Times, said all agencies will work "flat-out" to prepare to leave without an agreement on the future U.K.-EU relationship, and he hopes Brussels will reconsider its decision against reopening talks. "We still hope they will change their minds, but must operate on the assumption that they will not," he wrote. Gove will lead daily meetings — weekends included — of civil servants and advisers until ties with the EU are cut, the newspaper said.