Mayor Bill de Blasio finally announced Friday that he is backing Hillary Rodham Clinton for president, a much-discussed endorsement that had prompted some criticism from fellow Democrats for being so long in coming.

De Blasio said Clinton was the candidate best suited to navigate Washington and actually enact liberal policies to combat income inequality.

"The candidate who I believe can fundamentally address income inequality effectively, the candidate who has the right vision and the right experience to get the job done, is Hillary Clinton," the New York City mayor said during an early morning appearance on MSNBC's "Morning Joe."

The Associated Press and other media outlets reported Monday that de Blasio had, at last, decided to end the months of speculation surrounding his endorsement and would back Clinton.

The delay had long puzzled some political observers and frustrated some within the Democratic Party, including a few inside City Hall.

Some de Blasio advisors told NBC 4 New York the wait-and-see approach was not intended to elevate himself but to keep his party's focus on the progressive values he believes in so deeply.

The first-term mayor has long-standing ties to the Clintons. He worked in the Department of Housing and Urban Development under President Bill Clinton and was then plucked from relative political obscurity to run Hillary Clinton's successful 2000 U.S. Senate campaign.

He remained close to the couple, who appeared on stage with him at his January 2014 inauguration. President Clinton administered his oath of office.

But de Blasio appeared on "Meet the Press" the morning of Hillary Clinton's campaign announcement in April and said that unlike other New York politicians — including both U.S. senators and Gov. Andrew Cuomo — he would not automatically be backing the former secretary of state.

"I think she's one of the most qualified people to ever run for this office and, by the way, thoroughly vetted," de Blasio said then. "But we need to see the substance."

He stuck to that script in the coming months even as criticism mounted within the party. He also stuck to it during the rise of Democratic presidential candidate Bernie Sanders, who shares many of de Blasio's left-leaning views.

The mayor also moved toward making himself a national figure on liberal issues, particularly on the fight against income inequality, and founded The Progressive Agenda Committee, which is hosting a presidential forum in early-voting Iowa this December. (It's unclear which candidates may attend. Invitations go out next week.)

But polls reflected that many New Yorkers felt that de Blasio was prioritizing the national over the municipal, and many of his advisers inside and outside City Hall urged him to simply take the plunge and endorse Clinton.

On Friday, he finally did, choosing the day politicians traditionally use to dump less than flattering news and a week in which the city is distracted by the Superstorm Sandy anniversary and the Mets' World Series run. He offered a spirited defense of his former boss.

"There's a lot of spine there and a lot of steel there," said de Blasio. "She has said what she believes in. This is a very sharp, progressive platform, and she has the ability to follow through on it."

A Clinton spokesman did not respond to a request for comment about the endorsement. Instead, the campaign sent out an email to reporters touting the new support of 87 mayors across the nation.

Some of the mayors were quoted in the release. De Blasio, mayor of the nation's largest city, was listed fourth.