Twitter Inc boss Jack Dorsey said on Tuesday he will convert proceeds from the digital auction of the first ever tweet on the platform to bitcoin for charity.

"just setting up my twttr" - the first ever tweet went live for sale after Dorsey listed it as a unique digital signature on a website for selling tweets as non-fungible tokens (NFTs).

NFTs are digital files that serve as digital signatures to certify who owns photos, videos and other online media. Dorsey, a known bitcoin enthusiast, said the auction will end on March 21.

Payments company Square Inc, also led by Dorsey, invested $170 million more in bitcoin last month, adding to the mainstream acceptance of the digital currency that has been winning support from several big investors.

Dorsey's 15-year old tweet could attract bidders to pay a high price for the digital memorabilia. The highest bid for the tweet stood at $2.5 million as of 17:05 GMT on Tuesday.

The proceeds are being donated to GiveDirectly, a fundraising project to give cash directly to families experiencing extreme poverty in Africa.