Mr Raab said it was a “test of nerve” and his rivals would weaken the UK’s position in negotiations with Brussels by ruling out options to guarantee Brexit.
Critics of the approach have warned that prorogation would involve the Queen in a constitutional crisis, because formally it is the monarch who ends a session of Parliament.
Bur Mr Raab said it was unlikely to come to that because MPs’ powers to block a no-deal Brexit were limited.
Pointing to Institute for Government analysis, he said it would be much more difficult “for Parliament to engage in the guerrilla warfare sabotage of a government” that was resolved to leave by October 31.
“I think it’s wrong to rule out any tool to make sure that we leave by the end of October,” he told BBC Radio 4’s Today.
“The exam question in this contest is ‘who can be trusted to lead us out by the end of October and end this paralysing uncertainty’.”
Mr Raab said he would go back to Brussels with a “best, final offer” including the removal of the Irish backstop, but said there could be no further delay and the UK would be prepared to leave without a deal, falling back on World Trade Organisation rules.
“I think anyone who is talking about delay or who is taking WTO off the table is having the perverse effect of weakening our negotiating position in Brussels, that’s the lesson of the last three years,” he said.
“It’s a test of nerve here and if candidates cannot stand up their resolve to lead us out by the end of October in a leadership contest, what chance would they have under the heat of the negotiations in Brussels?”
Following Theresa May’s formal resignation as Tory leader, the starting gun has been fired for the race to replace her.
The nomination process will take place on Monday, with candidates requiring eight MPs to back them in order to enter the race, with the first round of voting on Thursday.