Donald Trump has said he will boycott the final Republican presidential debate before the Iowa caucuses.

The maverick Republican frontrunner accused Fox News debate moderator Megyn Kelly, whom he has clashed with in the past, of being a "lightweight".

The unexpected move prompted his closest rival, Senator Ted Cruz, to challenge him to a one-on-one debate.

Mr Trump's campaign manager announced the decision on Tuesday evening, with just 48 hours to go before the debate.

"He will not be participating in the Fox News debate Thursday," Corey Lewandowski said immediately after the press conference.

22 things Trump believes

The announcement followed a press conference in which Mr Trump lashed out at Ms Kelly, claiming she had been "toying" with him.

Mr Trump said he intended to hold a separate Iowa event at the same time as the debate to raise money for wounded veterans. Iowa hosts the nation's opening presidential primary contest on Monday.

"With me, they're dealing with somebody that's a little bit different," he said.
"They can't toy with me like they toy with everybody else. Let them have their debate and let's see how they do with the ratings."
'With or without'

On Tuesday night's airing of her Fox News show, The Kelly File, Kelly said the debate would "go on with or without Mr Trump".

A Fox News spokesperson said Mr Trump was still welcome to participate in the debate but would not be allowed to "dictate the moderators or the questions".

The Republican National Committee (RNC) said the decision was up to Mr Trump.
"Obviously we would love all of the candidates to participate, but each campaign ultimately makes their own decision what's in their best interest," said RNC chief strategist Sean Spicer.

Mr Trump had added an element of unpredictability to the Republican contest, and helped generate big ratings in the previous six Republican presidential debates.

His decision leaves seven other candidates in the debate: Texas Senator Ted Cruz, Florida Senator Marco Rubio, retired neurosurgeon Ben Carson, former Florida Governor Jeb Bush, New Jersey Governor Chris Christie, Ohio Governor John Kasich and Kentucky Senator Rand Paul.

The New York real estate mogul, who is in a tight race with Mr Cruz, has garnered media attention with provocative actions and statements, including a call for a temporary ban on all Muslim immigrants.