Bernie Sanders is challenging Democratic front-runner Hillary Clinton to schedule one more debate in April -- this time, in her home state of New York.

"I would hope very much that as we go into New York state, Secretary Clinton's home state, that we will have a debate -- New York City, upstate, wherever -- on the important issues facing New York and in fact the country," Sanders said Sunday in an interview with NBC News.

Asked if he was worried Clinton would no longer want to debate him, Sanders responded: "Yeah, I do have a little bit of concern about that. But I certainly would like to see a debate in New York state."

Get Breaking News Delivered to Your Inbox

In January, both Clinton and Sanders agreed to add more debates to the Democratic primary calendar. One, scheduled in March, was held in Michigan, per Sanders' request. The details of a May debate in California are also being worked on.

But in April, Sanders' campaign is pushing for a Democratic forum to take place in New York.

On Sunday, the campaign made the request official, when Sanders campaign manager Jeff Weaver sent a letter to Clinton's campaign manager, Robby Mook.

"Given the outcome of electoral contests since March 15, it is clearer than ever that New York will play a critical role in determining the Democratic nominee," Weaver wrote. "However, your campaign has consistently chosen to deny the people of New York the opportunity to see Senator Sanders and Secretary Clinton debate in the Empire State."

Weaver further questioned why the debate schedule had yet to be locked down.

"It is difficult to understand your motivation," Weaver told Mook. "Can you please explain why New York should not host the April debate? Is the Secretary concerned about debating before the people who twice elected her to the U.S. Senate? Perhaps there is some tactical advantage you are seeking by avoiding a debate in New York."

Sanders hopes to be competitive in the Democrats' New York state primary, scheduled for April 19. The state has 247 delegates up for grabs and is the largest nominating contest in the month of April.

On Saturday, Clinton's Democratic challenger pulled off landslide victories in three caucus states, with wins in Alaska, Hawaii, and Washington. Sanders still trails behind the former secretary of state, however, by hundreds of delegates.

The Clinton campaigned acknowledged that they had received Weaver's letter but declined to comment further.