Democratic presidential candidates Bernie Sanders and Hillary Clinton are consenting in principle to add four additional debates to the primary calendar, a Clinton campaign official confirmed to CBS News.

The agreed-upon debates, first reported by BuzzFeed News, are still under consideration by the Democratic National Committee (DNC), which officially "sanctions" every forum. All parties are still negotiating details of time and place.

The two candidates have also accepted the invitation of MSNBC and the New Hampshire Hampshire Union Leader, the state's largest newspaper, to attend an "unsanctioned" Democratic debate on Feb. 4. The New Hampshire debate would occur just days before voters turn out for the first-in-the-nation primary.

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Former Maryland Gov. Martin O'Malley, the third Democrat in the presidential race, has already expressed willingness to participate in any supplemental debates.

Earlier this week, Sanders campaign manager Jeff Weaver issued a statement calling for the DNC to arrange additional forums, shortly after Clinton committed to attending the last-minute New Hampshire debate.

"Sen. Sanders is happy to have more debates," Weaver said Wednesday. "But we are not going to schedule them on an ad hoc basis at the whim of the Clinton campaign. If Secretary Clinton wants more debates, that's great."

Weaver proposed that the extra forums be held in March, April, and May, with no debates scheduled for a Friday, Saturday, or holiday weekends.

On Saturday, Clinton's campaign called for one debate to take place in Flint, Michigan, where lead-poisoning in the city's water supply has left residents to deal with a public health crisis.

"We should use the spotlight of the presidential campaign to keep the focus on Flint, and to lift up the historic underlying issues that Flint and too many other predominantly low-income communities of color across America are struggling with every day," campaign chair John Podesta said in a statement. "We want their voices to be heard in this campaign, and holding a debate in Flint would go a long way toward achieving that goal."