Boris Johnson refused to be drawn on a potential Conservative party leadership bid when pressed on the subject in the run-up to the Tory conference.
The former foreign secretary was asked whether he might make the move when quizzed by the BBC.
In the broadcast, he said the Prime Minister was "a remarkable person" and that she will "go on for as long as she feels it necessary".
Mr Johnson, who is due to give a speech to conference on Tuesday, was asked repeatedly to rule out running against her.
He said: "The Prime Minister will go on, as she as she said to us herself, and as she said to the country, she's a remarkable person, she will go on for as long as she feels it necessary.
"But the most important thing for me is to avert what I think would be a political and economic disaster for this country which is to agree to come out of the EU but still to be run by the EU, what is the point of that, what will we have done?
"And I think there is still time for her to change course."
The comments followed a 4,500-word newspaper column on Friday which took a blistering attack on her Brexit strategy
After being asked repeatedly by the BBC, Mr Johnson refused to rule out voting against a deal based on Chequers in Parliament even if it meant bringing down the Government.
He also made a thinly-veiled jibe at Michael Gove, saying the idea of settling for a Chequers-type deal now that could be altered later was "complete pie in the sky".
This had been previously suggested by the environment secretary.
Mr Johnson also told Sky news that he refuses to apologise for comparing women wearing the burkha to 'letter boxes', accusing colleagues of whipping up 'confected indignation' over his comments.
