LONDON — Tesla CEO Elon Musk says his deal to buy Twitter can’t move forward unless the company shows public proof that less than 5% of the accounts on the platform are fake or spam.

Musk made the comment in a reply to another user on Twitter early Tuesday. He spent much of the previous day in a back-and-forth with Twitter CEO Paraj Agrawal, who posted a series of tweets explaining his company’s effort to fight bots and how it has consistently estimated that less than 5% of Twitter accounts are fake.

In his tweet Tuesday, Musk said: “20% fake/spam accounts, while 4 times what Twitter claims, could be much higher. My offer was based on Twitter’s SEC filings being accurate.”

He added that: “Yesterday, Twitter’s CEO publicly refused to show proof of 5%. This deal cannot move forward until he does.”

At a Miami technology conference Monday, Musk estimated that at least 20% of Twitter’s 229 million accounts are spam bots, a percentage he said was at the low end of his assessment, according to a Bloomberg News report.

Also at the All In Summit, Musk gave the strongest hint yet that he would like to pay less for Twitter than his $44 billion offer made last month.

He said a viable deal at a lower price would not be out of the question, according to the report by Bloomberg, which said it viewed a livestream video of the conference posted by a Twitter user.