With another GOP debate on the horizon - and the Iowa Caucus less than a week away - Republican frontrunner Donald Trump has chose to bow out of the event, scheduled for Thursday, Jan. 28.

An hour later, Trump's campaign manager Corey Lewandowski told The Washington Post that Trump would "definitely not" participate.

The press conference comes less than a week before Iowa's traditionally conservative Republican voters head to caucus sites and the same day a group of an anti-abortion leaders urged Iowans to oppose Trump's candidacy, suggesting inconsistencies on the issue.

A Fox News spokeswoman said Trump's decision is "rooted in one thing - Megyn Kelly, whom he has viciously attacked since August".

"The drama capped an increasingly heated war of words involving Mr Trump, Mrs Kelly and Fox News as the debate neared and as Mr Trump found himself facing the prospect of being questioned by her again before a national audience", The New York Times said.

Instead, Trump said, he will probably hold a type of fundraiser for veterans or wounded warriors.

The announcement went off like a bombshell in the presidential race, drawing condemnation from Fox and mockery from Trump's Republican opponents.

Trump responded by saying the problem was not with his remarks, but with people being too "politically correct". I think she, frankly, is not good at what she does.

Trump fired back as he has in recent days, calling Cruz "really a nasty person".

He added, "I don't' think Iowa's gonna care".

The comments are apparently at jab at Trump for polling his Twitter followers on whether or not he should participate in the debate. "Fox News is making tens of millions of dollars on debates and setting record ratings (the highest in history), where as in previous years they were low-rated afterthoughts", the campaign said in a statement.

"I think every candidate for president owes it to the voters, and in particular owes it to the men and women of Iowa, to go and humble yourself and put yourself before them and answer their hard questions", Cruz said. "Let's see how many people watch", Trump said. Nor does Cruz appear to have been hurt by Iowa Governor Terry Branstad's urging his fellow Republicans not to vote for the Texas senator.

Trump's blunt-spoken candidacy has boosted ratings for the Republican presidential debates.

Acknowledging the field is filled with honorable candidates, Cruz said the time has come for conservatives to rally behind the one campaign capable of taking on Trump in Iowa and preventing him from gaining additional traction.

In an interview with CNN this week, Trump said that he's "not 100 percent" set on going to Thursday's debate.