Former Mayor of New York Micheal Bloomberg has been a political independent since 2007.

He said in an Instagram post on Wednesday morning he has now registered as a Democrat.

Bloomberg considered running for president in 2016, and said on September 17 he could not run as a Republican.

Former New York Mayor and America's 10th richest man Michael Bloomberg says he has registered as a Democrat — 11 years after leaving the Republican party in 2007.

In an Instagram post on Wednesday morning he said he re-registered to the party he had supported for most of his early life because "Democrats provide the checks and balance our nation so badly needs."

Here's the post:

At key points in U.S. history, one of the two parties has served as a bulwark against those who threaten our Constitution. Two years ago at the Democratic Convention, I warned of those threats. Today, I have re-registered as a Democrat – I had been a member for most of my life – because we need Democrats to provide the checks and balance our nation so badly needs. A post shared by Mike Bloomberg (@mikebloomberg) on Oct 10, 2018 at 2:41am PDT Oct 10, 2018 at 2:41am PDT

On September 17 he said he would only run for president as a Democrat, Time Magazine reported.

He said: "I don’t see how you could possibly run as a Republican."

He considered running for president as an independent in 2016 but ultimately endorsed Hillary Clinton.

Bloomberg has had a long career in politics, and was Mayor of New York from 2002-2013.

He won the city's 2001 mayoral election running as a Republican, and was re-elected in 2005. But in 2007 he changed his registration to be an independent, and won the next election in 2009 with no party affiliation.

Wednesday's full statement on Instagram read:

"At key points in U.S. history, one of the two parties has served as a bulwark against those who threaten our Constitution. Two years ago at the Democratic Convention, I warned of those threats. Today, I have re-registered as a Democrat – I had been a member for most of my life – because we need Democrats to provide the checks and balance our nation so badly needs."

Bloomberg founded Bloomberg LP in 1981 and is the majority owner.