Musk has been locked in a bitter legal battle with Twitter since announcing in July that he was pulling the plug on his $44 billion purchase of the company.
A US judge has permitted Elon Musk to amend his complaint against Twitter, but rejected delaying the lawsuit over the disintegration of the billionaire's deal to acquire the social media company.
In a mixed ruling on Wednesday, Kathaleen McCormick, the chancellor of the Delaware court, said Musk could add whistleblowing revelations from a Twitter ex-security chief that surfaced in August.
But she denied his request to push back the litigation, saying prolonging the suit "would risk further harm to Twitter too great to justify."
Musk has been locked in a bitter legal battle with Twitter since announcing in July that he was pulling the plug on his $44 billion purchase of the company following a complex, volatile, months-long courtship.
Musk has said he canceled the deal because he was misled by Twitter concerning the number of bot accounts on its platform, allegations rejected by the company.
Revelations from Twitter's former security chief Peiter Zatko criticising Twitter's security practices first became public in August following a report in the Washington Post.
In a hearing on Tuesday, attorneys for Musk sought to amend his appeal and be granted additional time for document discovery to investigate Zatko's assertions.
Twitter attorneys argued Musk's request was another delay tactic designed to derail the takeover.
McCormick said Musk had cleared the relatively low legal bar to amend his complaint against Twitter, adding that she was "reticent" to weigh on the merits of Musk's arguments "before they have been fully litigated."
But she said Musk's side would be permitted "only incremental discovery" to follow up on the new allegations in light of the need for a speedy resolution of the case.
"The longer the delay until trial, the greater the risk of irreparable harm to Twitter," McCormick said, noting the company has suffered employee attrition while it "has been forced for months to manage under the constraints of a repudiated merger agreement."
The five-day trial is due to go ahead beginning October 17 in the Delaware court.