Michael Bloomberg rules out running for US president
Appearing on NBC television's Meet the Press programme, he said that those urging him to seek the presidency "should cease and desist".
Mr Bloomberg, 68, said he intended to remain focused on being mayor.
But he said he would continue to speak out on national issues that impact on New York, such as immigration.
Mr Bloomberg, who is in his third term as mayor, said: "The bottom line is that I've a great job."
He added: "I want to go out being, having a reputation as, a very good, maybe the greatest mayor ever."
While some of his backers have urged him to run, Mr Bloomberg said talk of a White House bid in 2012 came "because the press wants something to write about".
The founder of the Bloomberg news media empire, Mr Bloomberg is a former Democrat turned Republican turned independent.