Democratic Party chief Howard Dean says Barack Obama, Hillary Rodham Clinton and their supporters should beware of tearing each other down, demoralizing the base and damaging the party's chances of winning the White House in November.

In an interview with The Associated Press, Dean also said he hopes the Democratic nominee will be determined shortly after the voting ends in early June and that he will encourage the superdelegates who will play a role to make up their minds before the August convention in Denver. The 2004 presidential candidate told CBS News that he wants closure by the first of July. Dean said the charges and countercharges between Clinton and Obama have gotten too personal at times. He declined to say how they have crossed the line, but he said he's made it clear privately when it has happened.

"You do not want to demoralize the base of the Democratic Party by having the Democrats attack each other," he said Thursday during the interview in his office a t Democratic National Committee headquarters. "Let the media and the Republicans and the talking heads on cable television attack and carry on, fulminate at the mouth. The supporters should keep their mouths shut about this stuff on both sides because that is harmful to the potential victory of a Democrat."

After issuing a warning to Hillary Clinton and Barack Obama that negative campaigning threatens to tear their party apart, Democratic Party chair Howard Dean said the candidates need to keep their tone focused on winning the White House in November.

In a Friday interview on "Good Morning America," Dean cited record turnout but noted "some personal criticism" between the candidates.

"We have to keep our mind focused on the idea that at the end of the day we really need change in these country," Dean told ABC's Diane Sawyer. "One of these two candidates needs to win. We're going to win unless we divide ourselves and that, we cannot do."

Clarifying his role in resolving the tightly contested Democratic race, Dean said, "My job is to make sure we elect a Democratic president … That is what we're going to do. But we're going to do in in a unified way and we're going to do it with the consent and working together of both candidates."

Dean would not elaborate on his conversations with the candidates to the tone of their campaigns but said, "At the end of the day both of these candidates have an obligation to our country to support the other and make sure their supporters do as well."

"I am going to stand up for the rules, and I know I'm doing the right thing most of the time because I've got both Clinton people and Obama people mad at me," he said.