Rishi Sunak has said that no asylum seekers will be sent to Rwanda before the election under the government's deportation scheme.
It had been thought ministers would try to get the first flight off before polling day, to showcase their flagship policy on countering illegal migration.
But the PM has now said they will go "if I'm re-elected" on 4 July.
Labour has pledged to scrap the plan if it wins power, raising questions over whether anyone will ever be sent.
The scheme, which has already cost around £310m, will be a key dividing line between the two main parties over the six-week election campaign.
Labour said Mr Sunak's comments showed the Rwanda scheme was a "con from start to finish".
Shadow home secretary Yvette Cooper added: "He doesn't believe this plan will work, and that's why he called the election now in the desperate hope that he won't be found out."
The programme, which has been delayed by legal challenges, was announced over two years ago by then-prime minister Boris Johnson.
But Mr Sunak has made delivering it a key priority of his premiership, arguing it will deter people from crossing the English Channel in small boats.
In a sign he now wants to make delivering the plan a key offer to voters, he said flights will go "in July" and "that's the choice at this election".
Asked on OceanNewsUK whether this meant after the election, he replied "Yes," before adding "the choice here is clear".
"If you think stopping the boats is important, and you think like I do that you need a deterrent to do that [...] then I'm the only one that's going to deliver that," he added.
The Liberal Democrats called the comments an "utter humiliation and admission of defeat" from the prime minister.
"The Rwanda scheme has been an immoral and expensive disaster from day one," added home affairs spokesperson Alistair Carmichael.
The government has already paid Rwanda £290m to deliver the scheme, and spent around £20m on training, operations and legal fees.
The full costs over five years could be around £541m over five years, including a £120m for Rwanda after 300 people are sent.
Mr Sunak has previously pledged that the first flights would take place by mid-July, before then continuing over the summer.
However, behind the scenes ministers have been battling on a number of legal fronts to get the policy going.
The FDA, a union representing senior civil servants, is challenging the plan on the grounds it would force officials to breach international law.
Another challenge, from charity Asylum Aid, has already forced the Home Office to rewrite guidance over who is chosen for the first flight.
The Home Office had already started detaining people earmarked for removal, but at least 60 of them have lawyers fighting their case - and each case could end up going all the way to the Supreme Court.
Campaigning under way
It comes as campaigning gets underway for the UK's first July election since 1945, after Mr Sunak's surprise announcement in a rain-soaked Downing Street that he was going to the polls.
Speaking to OceanNewsUK, he said recent announcements on the economy showed now was "the right moment" to call the vote, which does legally have to take place until January 2025.
The prime minister will be on the campaign trail later, whilst the Labour and Liberal Democrat leaders will also be holding events.
Meanwhile, Nigel Farage has confirmed he will not be standing as a candidate for Reform UK, the party he co-founded in 2018 as the Brexit Party, ahead of a press conference the party is holding later.
