Defence Minister Peter Dutton is trying to amend his defamation claim against a refugee activist just two weeks ahead of his scheduled trial.
The Queensland MP is suing Shane Bazzi over the now-deleted tweet dubbing him a "rape apologist" and linking to a news article.
Mr Dutton is the only witness expected to give evidence during the trial, Justice Richard White told a pre-trial hearing on Tuesday.
The minister says the tweet defamed him and suggested he condones and excuses rape.
Mr Bazzi denies the charges but if found to have defamed the minister he pleads defences of honest opinion and fair comment.
Mr Dutton's barrister Nick Ferrett QC said the parties had been in agreement on Monday but his side had since decided to amend the statement of claim.
It was served on the defence about lunchtime on Tuesday just before the pre-trial hearing.
"I just simply have not had an opportunity of taking proper instructions," Mr Bazzi's lawyer Richard Potter SC said.
"It seems to be a mixture of particulars of aggravation and defeasance connected with what I would call post-publication conduct," he said.
"And secondly, an amendment of a little more substance in relation to aggravation concerning the apology of Senator Waters.
"There is no explanation at all for why that has suddenly changed."
Mr Ferrett said they could immediately provide to the court a draft amendment but did not think it necessarily useful ahead of the "amended defence".
He assured it would not expand the case beyond a "few tweaks".
Mr Bazzi's rape apologist claim was similar to an earlier statement by Greens Senator Larissa Waters, who has since retracted her claims and apologised.
The tweet included a link to a 2019 Guardian Australia article reporting comments by Mr Dutton that women refugees were "trying it on" by making claims they had been raped.
Mr Dutton told Sky News that female refugees held on Nauru were claiming they needed to come to Australia for an abortion following rape but changing their minds when they arrived.
"You could question whether people needed medical attention," he said at the time.
Mr Potter said they were applying to submit the full Guardian article in the proceedings as part of the defence case.
Justice White urged the parties in June to settle the dispute as the issues were confined, involved one document, and two defences pleaded.
He repeated that this was a matter capable of settlement.
"I will be asking for an assurance from you, not today, but an assurance that counsel had given their attention to a possible negotiated outcome to this litigation," he said.
In documents before the court, the MP claims he suffered hurt and embarrassment and was brought into "hatred, ridicule and contempt".
Due to COVID-19 restrictions, the three-day October trial will be held over Microsoft Teams.
The pre-trial hearing will resume on Thursday.
Australian Associated Press