Sen. Bernie Sanders' team is keeping up the pressure on Hillary Clinton's campaign to hold a debate in New York before the April 19 primary, and openly wondered whether Clinton was "afraid" to debate in the state Clinton once represented as a senator.

Sanders' campaign manager Jeff Weaver told MSNBC that while they held up their end of the bargain with earlier debates by holding debates in New Hampshire and Michigan, it's time that the Clinton camp do the same.

"This is not us demanding more debates, this is asking us to do what the Clinton people have already agreed to do," Weaver told Steve Kornacki. "It would be very, very dishonest for them not to do the debates they have promised to do. They promised to do one in March, we said let's do it in Michigan, that's where it happened. Another one coming up in April, and there's another one coming up in May."

"[W]e don't know why Secretary Clinton appears to be concerned about having a debate in New York. If we're going to have one in April ... why won't they have it in New York?" Weaver asked. "That's where Secretary Clinton was elected twice to the U.S. Senate. I just don't understand what the Clinton campaign is afraid of in terms of debating in New York."

The Clinton camp immediately fired back by echoing a call made Monday for Sanders to change his tone. Senior Clinton strategist Karen Finney said the Sanders campaign should decide against coming up with good "attack" lines against Clinton, and revert back to the positive campaign they were running earlier in the race.

"[Sanders] doesn't get to decide where and when he wants a debate," Finney said. "Let's go back to our process that had been working quite well, rather than trying to make this into kind of a gimmick. At the same time, they're trying to talk about how they're going to attack Hillary Clinton. I guess that's what we're saying."

She also noted that there have been conversations between the two sides, but that nothing is imminent.