NEW YORK (AP) — Ending months of delay that drew criticism from some fellow Democrats, New York City Mayor Bill de Blasio is planning to endorse Hillary Rodham Clinton for president, a person familiar with his plans told The Associated Press on Monday.

De Blasio is expected to make his endorsement official in the coming weeks and likely before a December presidential forum in early-voting Iowa put together by a political group founded by the mayor, according to the person, who was not authorized to speak publicly about the matter before the announcement and who spoke to the AP on condition of anonymity.

De Blasio managed Clinton's successful 2000 Senate campaign and has close ties to the ex-secretary of state and her husband, the former president, both of whom sat on stage for his 2014 mayoral inauguration.

Despite that, de Blasio had hesitated to back Clinton. The mayor said repeatedly that he wanted to hear more from Clinton on certain issues — namely income inequality — before he would offer his endorsement.

That left some Democrats accusing him of putting his own goals of becoming a national liberal leader ahead of party unity or loyalty to the Clintons.

"It's not clear to me that a town hall meeting in the cornfields of Iowa has anything to do with the quality of life of everyday New Yorkers," Rep. Hakeem Jeffries, D-N.Y., said earlier this fall, questioning the mayor as he offered his own endorsement of Clinton.

De Blasio has publicly been inching toward the endorsement in recent weeks. He had praised her stances on a number of issues, including criminal justice reform and, earlier this month, her opposition to the Trans-Pacific Partnership trade agreement.

"I think she's running a very good campaign because her vision is getting stronger and stronger," de Blasio said recently. "There are a few more areas I want her to flesh out in her vision, but I think she's been doing a great job."

A spokesman for Clinton confirmed that aides for the candidate and the mayor have held discussions but declined further comment. News of those talks was first reported by Politico New York on Monday.

Earlier Monday, Clinton's camp announced the support of 100 leaders from New York. De Blasio's name was not on the list, though most prominent New York politicians, including the mayor's frequent rival Gov. Andrew Cuomo, were on the roll call.

De Blasio founded The Progressive Agenda Committee, which is largely comprised of left-leaning politicians and activists, this spring to call attention to issues such as paid sick leave, universal prekindergarten and reining in the national debt. It is holding a forum for presidential candidates Dec. 6 at the University of Iowa.

None of the candidates have officially committed to attending the forum, though some — including Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O'Malley — have previously expressed interest. The Clinton spokesman declined to say whether she would attend.