The European Research Group (ERG) chairman sought to dampen expectations over the prospect of a leadership contest, following days of fevered speculation over whether enough Conservative MPs had submitted no-confidence letters in the prime minister.
Mr Rees-Mogg insisted "patience is a virtue, virtue is a grace" when pressed on whether the necessary 48 letters had been sent to force a confidence vote at an event in Westminster.
However he warned his colleagues that a confidence vote now might be their only chance to remove Ms May the next general election.
Tory rebel organiser Steve Baker said it was "now or never" to oust Ms May and characterised the move as an "insurrection by a group of determined democrats" against the "might of the state".
It comes after Mr Rees-Mogg issued a rallying call to other Tory MPs to topple the prime minister last week, when he joined around 26 Conservative backbenchers in publicly submitting no-confidence letters to Sir Graham Brady, of the 1922 committee.
Asked why the threshold had not been met, he said: "Patience is a virtue, virtue is a grace. We will see what letters come in due time.
"Do 47 want to come with me or not? I may find that they don't or they don't do it today but when we get the meaningful vote. That's a decision for them."
The North East Somerset MP admitted it had been "quite difficult" to get the number and warned that time was running out for rebels to act.
Asked if they would struggle to secure the votes, he told reporters: "I would wait and see about that. You speak to Tory MPs and find Tory MPs who say they are really keen that Theresa May should lead us into the next general election.
"Basically, if there is a vote of confidence it is not just for a year. Getting the 48 letters has shown to be quite difficult, so the idea that in a year you just repeat the process and then she would go at that point I don't think that is realistic.
"I think it is now or the prime minister will lead the Conservatives into the next election.
"You find MPs privately who will say to you they think that is a really good idea in any number and I would be quite surprised."
He also told ConservativeHome earlier, that some people don't want a leadership vote but "would like it when the meaningful vote comes up and think that is the time to put in letters."
Mr Baker, a former Brexit minister, said it was a “grave decision” to trigger a leadership bid and he had “considerable sympathy” with wavering MPs.
He added: “Let’s not forget we are up against the full might of the state and the Tory Party. The state and the Tory Party are not timid or incompetent organisations when it comes to political organisation.
“This is an insurrection by a small group of determined democrats to deliver a Brexit worth having and we are fighting enormously powerful and well-organised forces who are not stupid, and occasionally they will have a small victory.”
The remarks came at an ERG event to launch a "myth-busting" dossier on post-Brexit customs rules, which said most of the problems ascribed to leaving the customs unions are “imaginary” or “exaggerated”.