WASHINGTON (REUTERS) - US presidential candidates Bernie Sanders and Donald Trump have appeared to agreed to debate each other ahead of California's June 7 primary contest, an unconventional move before either political party has formally picked its nominee.

Sanders, a US senator from Vermont, is still locked in a tight primary battle against Democratic front runner Hillary Clinton, while Trump effectively clinched the Republican party's nomination earlier this month when his two remaining rivals dropped out.

In an appearance on ABC's "Jimmy Kimmel Live" late Wednesday, Trump was asked whether he was willing to participate in such an event against Sanders.

"Yes, I am," Trump said, adding that he would do it if the event's proceeds were donated to a good cause.

"If I debated him, we would have such high ratings," the billionaire businessman said. "I think I should... take that money and give it to some worthy charity."

Sanders appeared to agree in a post on Twitter early Thursday. "Game on," he tweeted. "I look forward to debating Donald Trump in California before the June 7 primary."

Representatives for both campaigns did not immediately respond to requests for comment, and neither campaign has released any formal plans for such a debate.

Kimmel said he asked Trump about the debate at Sanders'suggestion. Sanders, who is scheduled to appear on the show Thursday night, had first challenged Clinton to a California debate and said he was "disappointed" when the former secretary of state declined.

The Clinton campaign did not immediately respond to a request for comment.