In the op-ed, Bloomberg admitted that being a 2016 presidential candidate is “not a risk” he could take “in good conscience."
He added: “I could not win. I believe I could win a number of diverse states -- but not enough to win the 270 Electoral College votes necessary to win the presidency.”
"I love our country too much to play a role in electing a candidate who would weaken our unity and darken our future -- and so I will not enter the race for president of the United States," Bloomberg wrote.
Bloomberg also used his op-ed to attack Donald Trump, arguing the Republican front-runner "appeals to our worst impulses" and he is running the "most divisive and demagogic presidential campaign I can remember."
He wrote that he's not ready to endorse a candidate yet.
Bloomberg had toyed publicly with a run since January, deliberating about the dollars and infrastructure required for ballot access in all 50 states.
A source close to Bloomberg told ABC News last week that that the odds of Bloomberg running for president were “very, very low -- almost zero."