President Obama mocked Republican presidential candidates after they complained last week's CNBC debate was designed to pit candidates against one another and requested new rules for future debates.

"Every one of these candidates say, 'Obama's weak. Putin's kicking sand in his face. When I talk to Putin, he's going to straighten out,'" Obama said at last night's Democratic fundraiser in New York.

"They can't handle a bunch of CNBC moderators ... If you can't handle those guys, then I don't think the Chinese and Russians are going to be too worried about you."

Republican candidates Donald Trump, Carly Fiorina, John Kasich and Chris Christie say they will not sign a memo listing debate rules.

Trump reacted reacted to the President's remarks on "Fox and Friends."

Trump said that Obama is "good with ad libs, but has done a terrible job as president."

Watch the President's remarks above and Trump's appearance below.

WATCH: Cruz Blasts GOP Debate Moderators' Bias

Trump: 'Very Beautiful' to See Candidates Unite Against Biased Moderators

Carson: 'Sick and Tired' of Media Trying to Formulate People's Opinions

Priebus: 3rd GOP Debate Was 'Nothing But a Crap Sandwich'