Bloomberg has prepared the groundwork for a possible bid for the Democratic nomination in recent weeks, including registering as a candidate in the states of Alabama, Arkansas and Texas.
A message on his website mikebloomberg.com says the site is "paid for by Mike Bloomberg 2020." Ten days ago he said he was "close" to making a final decision on whether or not to enter the crowded field.
His personal fortune of $50 billion means a Bloomberg candidacy would likely shake up the open race, with 17 candidates already vying to be the Democratic nominee to take on President Donald Trump next year.
Bloomberg's advisors have said that if he does run then he will probably not campaign in the four states that will hold primaries in February.
Instead, he would focus on the 15 primaries scheduled for March 3, known as "Super Tuesday," including the most populous states of California and Texas.
Former vice president Joe Biden leads the race ahead of left-wingers Elizabeth Warren and Bernie Sanders, with moderate Pete Buttigieg in fourth place, according to national polls.