The leadership hopeful said if he becomes the new prime minister, he would “engage” with other EU leaders throughout August, and task a new negotiating team with producing an “alternative exit deal”.
But he warned he would be ready to walk away from talks if there was no “immediate prospect” of progress and increase preparations for a no deal Brexit.
The Foreign Secretary said: “It is important that the EU knows that we will do what it takes to make a success of a no-deal Brexit.
“We won’t blink as a country. That no-deal Brexit is not going to be an opportunity for them to successfully turn the screws on our country.
“I will start engaging with the EU straight away, throughout August.
“Then, when we have published our plan for a deal we think we can get through Parliament by the end of August, we will start formal negotiations in September.”
Mr Hunt added: “There is a hard deadline in what I have said, by the end of September, I, as Prime Minister, will make a judgment as to whether there is a realistic prospect of a deal that can get through Parliament in the short-term.
“And, if my judgment is that is not the case, talks will stop and we will put our heads down and focus on no-deal.”
But Mr Hunt and Mr Johnson’s no deal Brexit plans have suffered a major blow after Chancellor Philip Hammond warned there would be no extra money to spent if the UK left the EU without an agreement in place.
Both leadership candidates have made costly pledges as they vie to replace Theresa May as the next Prime Minister.
Mr Hammond told them the “fiscal firepower” that has been stocked up will be needed entirely to counteract the effects of leaving without a deal.
He warned: “The ‘fiscal firepower’ we have built up in case of a no-deal Brexit will only be available for extra spending if we leave with an orderly transition.
“If not, it will all be needed to plug the hole a no-deal Brexit will make in the public finances.”
In a speech earlier today, Mr Hunt said a Government led by him as Prime Minister would cover the costs of tariffs that would be imposed on the farming and fishing industries.
He has pledged to establish a “no deal relief programme” and also set up a no deal committee to ensure the Government is ready to leave by the October 31 deadline.
Mr Hunt said: “If you’re a sheep farmer in Shropshire or a fishermen in Peterhead I have a simple message for you. I know you face uncertainty if we have to leave the EU without a deal.
“I will mitigate the impact of a no-deal Brexit on you and step in to help smooth those short-term difficulties.
“If we could do it for the bankers in the financial crisis, we can do it for our fisherman, farmers and small businesses now.”