He acknowledged there was "reluctance" in Europe about his demands for the backstop - the plan to prevent a hard border with Ireland in all circumstances - to be scrapped.
"There may well be bumps in the road but we will be ready to come out on October 31 deal or no deal," Mr Johnson said during a visit to Truro.
"Now of course our friends and partners on the other side of the Channel are showing a little bit of reluctance at the moment to change their position.
"That's fine - I'm confident that they will - but in the meantime we have to get ready for a no-deal outcome."
Fresh concerns have been raised about the prospect of a no-deal Brexit following the leak of a confidential Whitehall dossier on the Operation Yellowhammer contingency plans.
Published by the Sunday Times, the “Operation Yellowhammer” documents warn that Britain will be hit with a three-month “meltdown” at its ports, a hard Irish border and shortages of food and medicine if the UK leaves without an agreement.
Mr Johnson, when asked about the Operation Yellowhammer documents, said: "I'm not going to suggest that there won't be - as I said on the steps of Downing Street - there may well be bumps in the road but we will be ready to come out on October 31 deal or no deal."
A senior Whitehall source told the Sunday Times: “This is not Project Fear, this is the most realistic assessment of what the public face with no deal. These are likely, basic, reasonable scenarios – not the worst case.”
A Downing Street spokeswoman said the leaked no-deal Brexit dossier was "out of date" and "we are making all necessary preparations ahead of October 31".
According to the documents, petrol import tariffs would “inadvertently” lead to the closure of two oil refineries, while protests across the UK could “require significant amounts of police resources” in a no-deal scenario.
They also warn that Gibraltar could face delays of up to four hours at the border with Spain for “at least a few months”.
But a Number 10 source said: “This document is from when ministers were blocking what needed to be done to get ready to leave and the funds were not available.
“It has been deliberately leaked by a former minister in an attempt to influence discussions with EU leaders.
“Those obstructing preparation are no longer in Government, £2 billion of extra funding (has been) already made available, and Whitehall has been stood up to actually do the work through the daily ministerial meetings.
“The entire posture of Government has changed.”
Michael Gove, the Cabinet minister responsible for no-deal planning, insisted Yellowhammer represented a “worst-case scenario” and said “significant” steps have been taken in the last three weeks to accelerate Brexit planning.
Following the leak Hilary Benn wrote to Mr Gove asking him to appear in front of the Committee on exiting the European Union, of which he is chair.
Mr Benn is seeking clarification on several issues regarding Brexit preparedness.
Johnson’s planned meetings with the French president and German chancellor come ahead of the G7 summit in Biarritz at the end of the week, where the PM is likely to meet US president Donald Trump for talks.
Ahead of that meeting, Mr Johnson spoke on the phone with Irish premier Leo Varadkar and the pair "shared perspectives on the Withdrawal Agreement".
A Downing Street spokesperson said: "The Prime Minister indicated that the Withdrawal Agreement in its current form will not get through the House of Commons, that the backstop would need to be removed, and that an alternative solution is required.
"The Taoiseach reiterated the EU27 position that the Withdrawal Agreement cannot be reopened, and emphasised the importance of the legally operable guarantee to ensure no hard border and continued free trade on the island of Ireland."
During a press briefing the EU said the UK would be worse hit by a no-deal Brexit than the trading bloc.
EU Commission deputy chief spokesperson Natasha Bertaud said an exit without the Withdrawal Agreement would cause "significant disruption both for citizens and for businesses and this will have a serious negative economic impact."
She added how this would be "proportionally much greater in the United Kingdom than it would be in the EU 27 states."
When asked whether progress would be made during upcoming talks with Ms Merkel and Mr Macron, Mr Johnson replied: "Well that is, I'm afraid, very much up to our friends and I hope that they will compromise.
"They have seen that the UK parliament has three times rejected the Withdrawal Agreement, the backstop just doesn't work, it's not democratic and I hope that they will see fit to compromise but in the meantime we get ready to come out on October 31."
Meanwhile, the Daily Telegraph reported that up to 40 Tory MPs are backing a bid led by former Cabinet ministers Philip Hammond and David Gauke to stop a no-deal Brexit on October 31.
Last week the former chancellor and 20 other senior Tories were said to have written to the PM to say his demands to abolish the backstop “set the bar so high that there is no realistic probability of a deal being done”.