Hillary Clinton on Jan. 28 seemed to acknowledge that Bernie Sanders was an increasingly viable challenger for the Democrats' 2016 White House nomination when she said she was ready to show up for a debate on Feb. 4 in the crucial primary state of New Hampshire.

But the former secretary of state avoided an explicit commitment to three more such encounters, which Sanders has suggested, CNN reported.

Sanders Wants Debates in March, April, May

"We have another (debate) shortly after New Hampshire on the calendar, and I've said we should start looking for dates to get one scheduled. I'm perfectly fine with that," Clinton told the news channel.

"But first things first: We have to agree that we're going to debate in New Hampshire. Both (former Maryland Gov. Martin O'Malley) and I have agreed, and we're waiting for (Sanders) to decide to join us."

The Vermont senator, meanwhile, had suggested on Jan. 27 that he would only be part of the Granite State event if Clinton, in turn, accepted three additional debates in March, April and May, Politico noted.

"From the beginning of this campaign, Sen. Sanders has called for more debates," the lawmaker's campaign manager, Jeff Weaver, said in a statement.

"Secretary Clinton has not. Now she is asking to change the rules to schedule a debate next week that is not sanctioned by the DNC. Why is that? The answer is obvious. The dynamics of the race have changed, and Sen. Sanders has significant momentum."

Sanders Resists Scheduling by 'Whim of the Clinton Campaign'

Part of the discussion surrounding the Feb. 4 debate in New Hampshire, meanwhile, has to do with the fact that the event, to be hosted by the Union Leader newspaper in collaboration with MSNBC, has not been sanctioned by the Democratic National Committee (DNC), CBS News explained.

Symone Sanders, a spokeswoman for Sanders, had initially argued that candidates risked being barred by the DNC from future encounters if they chose to participate in unofficial debates.

"Sen. Sanders is happy to have more debates but we are not going to schedule them on an ad hoc basis at the whim of the Clinton campaign," Weaver added in his statement.