Philip Hammond has communicated to the BBC He intends to resign as Chancellor in case Boris Johnson becomes the next Prime Minister of the UK.
He said a Brexit without agreements, something that Mr. Johnson has left open as an option, is "not something I could ever agree with".
Asked if he believed he would be released next week, Hammond said he would step down with Theresa May on Wednesday.
He said he intends to stop following the prime minister's questions, but before Ms. May resigns.
In the BBC broadcast Andrew Marr, Mr. Hammond said it was important for the next prime minister and his chancellor to be "closely aligned" with Brexit policy.
Mr. Johnson has said Britain must leave the EU by the new deadline for Brexit on October 31
Mr. Hunt has said that a no-deal exit can not be ruled out, but he is ready to extend Britain's EU membership if needed for a new Brexit deal.
Mr. Hammond said the situation "could be more complicated" if Jeremy Hunt wins the Tory leadership competition, but "all polls" suggested Mr. Johnson would be successful.
"That's what's likely to happen, and I make my plans accordingly," he said, adding that he would wait until Tuesday's result to "be safe."
Mr Hammond said that he understood that the commitment to leave by that date, even if no agreement had been reached, would be a condition for the Office in Mr Johnson's Cabinet.
He said, "I can never sign that, it's very important that a prime minister has a chancellor who works closely with him on politics."
He added that Jeremy Hunt's position on a no-deal Brexit was "nuanced," and he had not demanded a "loyalty pledge" on future ministers' exit days.
Mr. Hammond said he would support both men in the pursuit of a new Brexit agreement, but it would not be possible to agree this before the end of October.
"A true pursuit of a deal will take a little longer," he added.
Mr. Hammond was a well-known critic of the idea of a no-deal Brexit, who recently announced that he might vote to overthrow the next prime minister to stop such a scenario.
He had said he could "not rule anything out" when asked if he would support a motion of censure against the government.
When asked if he would vote against the next prime minister with a vote of no confidence, he said, "I do not think that will happen."
"I am confident that Parliament has a way to prevent this without parliamentary approval on October 31, a no-deal exit."
"I intend to work with others to make sure that Parliament use his power to make sure the new government can not, "he added.
Earlier, Justice Secretary David Gauke reaffirmed his intention to resign from the government if the next prime minister seeks a consensual Brexit commitment to support no-deal on October 31 – which Boris, to be honest, keeps saying – I am not ready to join this.
Meanwhile, the Irish Deputy Prime Minister said that the Irish Republic has "no choice" but to protect its place in the EU single market, when the United Kingdom "imposes a Brexit on all others without an agreement."
In the BBC Andrew Marr warned Simon Coveney: "If the incoming conservative prime minister decides to" rip "the Brexit withdrawal treaty, then" we're in trouble. "
" That's a bit like saying, "Give me that whatever I want or I will burn down the house for all. "
The ballots must be returned on Monday until 17:00 CET. The winner of the competition will be announced on Tuesday.