The government is insisting the UK will still leave the EU by 31 October, despite a letter sent to Brussels asking for a delay.
Boris Johnson sent the letter 'unsigned' after a major setback in the Commons to his Brexit strategy.
But the request was accompanied by a second letter, signed by the PM, saying he believed a delay would be a mistake.
Senior minister Michael Gove told Sky News the government had "the means and ability" to leave on 31 October.
His colleague, Foreign Secretary Dominic Raab, told the BBC's Andrew Marr the prime minister had "proved the doubters wrong" by securing a new Brexit deal with Brussels and he was confident the UK would still leave on Halloween.
EU Council President Donald Tusk has acknowledged receipt of the UK's extension request and said he would consult EU leaders "on how to react".
Mr Johnson has spoken to fellow leaders and Mr Tusk, telling them the letter "is Parliament's letter, not my letter".
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Michael Gove, who as chancellor of the Duchy of Lancaster is in charge of no-deal planning, said "the prime minister's determination is absolute" and the government's "determined policy" was to meet that deadline.
'We know that the EU want us to leave, we know that we have a deal that allows us to leave,' he told the Sophy Ridge programme.