Elon Musk has given the strongest hint yet that he would like to pay less for Twitter than his $US44 billion ($63 billion) offer made last month.

The Tesla chief executive told a Miami technology conference that a viable deal at a lower price would not be out of the question, according to a report by Bloomberg News, which said it viewed a live-stream video of the conference posted by a Twitter user.

Also at the All In Summit, Mr Musk estimated that at least 20 per cent of Twitter’s 229 million accounts were spam bots, a percentage he said was at the low end of his assessment, according to the report.

The appearance came a few hours after Mr Musk began trolling 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 per cent of Twitter accounts were fake.

The day’s events bolstered theories from analysts that Mr Musk either wants out of the deal or is seeking a lower price, largely due to a huge decline in value of Tesla stock, some of which he has pledged to finance the Twitter acquisition.

Twitter shares closed on Monday down just more than 8 per cent at $US37.39. That is below where the stock was just before Mr Musk disclosed that he was Twitter’s largest shareholder.

Mr Musk made the offer to buy Twitter for $US54.20 a share on April 14.

On Friday, Mr Musk tweeted that his plan to buy Twitter was placed on temporary hold as he tried to pinpoint the number of fake accounts on the social media platform.

He said the hold was pending details of Twitter’s calculation that fake accounts were less than 5 per cent of its users.

In tweets on Monday, Mr Agrawal acknowledged Twitter was not perfect at catching spam, but every quarter the company estimated there was less than 5 per cent of it.

Mr Musk responded with a smiling emoji of poop, then asked how Twitter’s advertisers knew what they were getting for their money.

Tesla shares closed down nearly 6 per cent at $US724.37. They have lost about one-third of their value since the trading day before Mr Musk disclosed his Twitter stake.