SoftBank founder Masayoshi Son took to Twitter on Wednesday to offer a million free coronavirus tests, only to get hit by a barrage of criticism that he risked overwhelming medical facilities, prompting him to say he might reconsider the plan.

The SoftBank Group chief executive, who last posted on Twitter three years ago, expressed concern about the coronavirus outbreak, telling Twitter followers on Tuesday he was planning to take action.

"I would like to provide the opportunity for free PCR testing for those who are worried about the novel coronavirus," Son tweeted on Wednesday. "First, for 1 million people. We are preparing how they can apply," he said, referring to polymerase chain reaction (PCR) tests which can detect very early infections.

His proposal was met with criticism that it would overburden medical facilities and workers.

Son said he had visited the health ministry on Wednesday as he wanted to cooperate so that the testing would not cause any burden.

He also tweeted an illustration of the PCR plan under consideration, in which a person could take a nasal swab at home and mail it to a lab that would test the specimen send back the results.

But about two hours after his first tweet announcing the PCR test plan, he took to Twitter again to say he might reconsider given the negative feedback.

"Since it's been badly received, maybe I won't do it ..." he said.

The coronavirus has spread around the world, with more than 116,000 confirmed cases and 4,000 deaths.

Japan has reported close to 1,300 infections, with more than half coming from the quarantined Diamond Princess cruise ship.