NEW YORK (CBSNewYork) – Mayor Bill de Blasio is staying mum.

During an appearance on ABC’s This Week, the mayor explained why he hasn’t endorsed Hillary Clinton, Bernie Sanders or anyone else yet in the 2016 presidential race.

De Blasio served as Hillary Clinton’s campaign manager during her first bid for U.S. Senate.

“I’m very proud to be a Democrat right now, because the Democratic field is talking about income inequality, talking about how to help working families, how to restore the middle class, talking about progressive taxation, I think quite honestly and forthrightly,” de Blasio said. “The Republican field is not only attacking each other, they are offering very divisive visions about this country that I think are actually going to turn off a lot of the American people.”

De Blasio praised Clinton’s campaign, despite her recent slip in the polls.

“I think she’s running a very good campaign because her vision is getting stronger and stronger,” de Blasio said.

So what will take for de Blasio to make his decision?

“It’s like any other endorsement decision. Look at the vision, look at the facts, look at the capacity. Hillary Clinton is an extraordinarily capable person. I know this from personal experience. There are few more areas I want her to flesh out in her vision, but I think she’s been doing a great job,” de Blasio said. “I think the issue of wages and benefits we need to hear a little more on. Certainly on the trade issue. But I do want to say she announced she has consistently put forward a stronger and stronger vision, literally each week, and that’s very encouraging to me.”

De Blasio said he doesn’t think Joe Biden should enter the race.

“I think we have great candidates right now. I really do. I’m very comfortable with the candidates we have. I think the Democratic debate is a constructive, positive one. I think with the candidates we have we’ll do very well,” he said.