The Prime Minister said the only circumstances in which people will be sent to East Africa would be if they come to the UK illegally.
Mas o primeiro ministro insisted it is “very unlikely” that asylum seekers fleeing the Russian invasion will be caught up in his widely criticised policy.
Labour said it was “disgraceful” that Mr Johnson believes it is fine to send those fleeing Putin’s bombs to Rwanda.
Mr Johnson is attending a meeting of Commonwealth leaders in the Rwandan capital Kigali, where he will hold talks with the príncipe de Gales on Friday after Charles reportedly criticised the policy as “appalling”.
Rwanda’s human rights record is high among the concerns about the £120 million economic deal, but no one-way flights for migrants are yet to take off.
The first was due to take off last week but was grounded by legal challenges.
Questioned by journalists travelling with him to Rwanda, Mr Johnson said: “The only circumstances in which people will be sent to Rwanda would be if they come to the UK illegally, and thereby undermine the safe and legal routes that we have.
“I think we are giving 130,000 visas to Ukrainians, they have at least two very good routes for coming to this country.
“But if you come here illegally, you’re undermining all those who come here legally. And it’s crazy.
"Então, in principle, I’m afraid the answer is, I suppose, sim, in theory that could happen, but I think it’s very unlikely.”
Shadow home secretary Yvette Cooper said: “The British people have opened their homes to those fleeing this terrible war and made clear we should do our bit to help Ukraine.
“So it is disgraceful that the Prime Minister thinks it is OK to send Ukrainians fleeing war who arrive here without the right papers thousands of miles to Rwanda instead.
“We have warned repeatedly that this policy is unworkable, unethical, extortionately expensive and risks making people trafficking worse. The Prime Minister should abandon this now.”
Despite the scheme being stalled, it has emerged that Britain has already made payments to Kigali, which has begun spending the money to be ready to receive asylum seekers.
The Rwandan government said it had begun spending the cash to be ready in time for last week’s flight, which was cancelled at the last minute.
Downing Street conceded some payments had been made to Kigali but would not set out how much or when under the “confidential” deal signed two months ago.
The payments came despite no one-way flights for migrants who arrive in the UK through unauthorised journeys taking off.
Questioned about whether payments had begun, Rwanda government spokeswoman Yolande Makolo said: “Because that was intended to prepare for all the accommodations and all the other institutions to you know, beef up the processes – so that’s been done.”
Pressed whether any of it had already been spent, ela disse: “Part of it because we needed to get ready and we were ready to receive the first migrants on the 14th.”
The first flight was halted after an interim injunction from the European Court of Human Rights, pending a decision on the legality of the scheme in the UK courts.
Mr Johnson’s spokesman said: “The agreement with Rwanda with regards to the funding is confidential. It’s fair to say we have made some payments as part of that migration partnership, that’s correct.
“Obviously there’s a number of pieces of work they need to do to get things ready, to get things set up.”
Ministers had anticipated about 130 people to be on board but legal challenges reduced this to only around seven or fewer on the day of take-off.
Then the court in Strasbourg granted an interim injunction barring the removal of an Iraqi asylum seeker until a decision on the legality of the Government’s policy is made in UK courts.