The actor echoed similar sentiments about the movie's script during an appearance on US TV show Live! With Kelly, reports The Insider.
"We have to get it right," he said, adding that "there's danger for humiliation" if the script isn't up to scratch.
Grant also told Total Film last month that the sequel is still on the boil.
"That film is not really on yet. We are up for it, but they haven't quite cracked the script. But when they do, I'm sure we'll make it," he said.
"I did like playing Daniel Cleaver in both films, but there is no definite part three," he told the magazine.
"None of the three of us have signed up for it yet. There's been a number of drafts that have had great things in them but haven't quite hit the bullseye. It's just that it does have to be significantly reinvented.
"I don't think that you could pretend that it's a year after the end of the last one because we look f***ing ancient now, all three of us," he added.
Working Title Films, the production company behind the project, acknowledged in February that production on the sequel had been delayed because of script problems.
"We are still working on the script, hence the delay to the start of production, but the film is going ahead as planned," said Working Title chairman Tim Bevan.
The third instalment will see Renee Zellweger reprise her role as the hapless, chardonnay-swilling singleton.
Colin Firth is also set to return as Mark Darcy. He spoke about a potential plot for the sequel last year.
"I can tell you that Bridget and Mark can't have children, I think that's the way it goes on," Firth told Access Hollywood. "So then she makes the huge mistake of going back to Daniel Cleaver for long enough to get pregnant. And I think he dumps her, and she's left stranded, and guess who comes back to rescue her?"
Firth added: "There's a script. This character has obviously inhabited part of my life. I'm always interested to see where it's taken, and it does look as if it's going somewhere interesting."
Bridesmaids' Paul Feig was originally lined up to direct the project, but he dropped out last October amid creative differences with Working Title, according to the Hollywood Reporter.
The Full Monty's Peter Cattaneo will direct, while author Helen Fielding is co-writing the screenplay with David Nicholls.
Fielding revealed last year that she is working on a third Bridget novel, as well as working on a script for the third film.
"It's hard to pull these things together," she said of the much-delayed movie. "There are so many people involved. I think they are sort of moving towards it now. It's definitely taking shape now, and it would be so much fun if they all came back and did it. You know, Colin has won an Oscar now. No pressure or anything."
Zellweger's spoken of her interest to bring Bridget out of retirement before, but said the idea of padding out for the role was daunting.
She said in 2007: "Can I just tell you my body is whacked by the time we finish one of those. It doesn't know what has happened because it thinks there's supposed to be a baby and there's no christening.
"Did you see that movie about fast food, Supersize Me?
"I had a panic attack with all the specialists talking about how bad this is for you, long term, putting on that much weight in short periods of time and they're all saying, 'You must stop this now or you will die'."
The first film, Bridget Jones's Diary, was a hit when it was released in 2001, taking in US$281 million at the box office. The sequel, Bridget Jones: Edge of Reason, released in 2004, opened to fairly negative reviews, but went on to earn US$262 million worldwide.
Speaking of sequels...
A Top Gun sequel is officially in development.
As I reported back in December, Tom Cruise said he was on board for a follow-up to the 1986 blockbuster providing they "find a story that [they] all want to do".
Well, it looks like Top Gun 2 is about to take-off, according to word from Paramount Film Group president Adam Goodman.
Asked about making another Mission: Impossible, he said: "We'll likely make a Top Gun sequel with Tom Cruise first," he told the Hollywood Reporter.
"Jerry Bruckheimer would produce, with Tony Scott returning to direct. All parties are moving ahead."
Meanwhile, Disney has announced that Kermit, Miss Piggy and the rest of the Muppet gang will be making a return to the big screen.
The studio confirmed a sequel to last year's The Muppets movie at the CinemaCon convention in Las Vegas this week, reports the BBC.
James Bobin will return to direct. As previously reported, Jason Segel, who starred in The Muppets, won't be taking on scripting duties in the sequel.
No word on a release date yet.
* Do you want to see another Bridget Jones movie? Chime in below, readers.
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