The world would be a better place if dictators such as Saddam Hussein and Muammar Gaddafi were still in power, top Republican US presidential hopeful Donald Trump said in comments aired Sunday.

The billionaire real estate tycoon also told CNN's State Of The Union talk show that the Middle East 'blew up' around US President Barack Obama and former secretary of state Hillary Clinton, his biggest Democratic rival in the race for the White House.

'One hundred percent,' Trump said when asked if the world would be better off with Saddam and Gaddafi still at the helm in Iraq and Libya.

Trump (pictured in Miami on Friday) said that the Middle East is worse now than when Huddein and Gaddafi were in power

Trump said on Sunday that dictators like Saddam Hussein (left at moment of his capture) and Muammar Gaddafi (right) would '100 percent' make the world a better place if they were still in power

Both strongmen committed atrocities against their own people and are now dead. Saddam, the former Iraqi president, was toppled in the 2003 US-led invasion of Iraq and was executed in 2006.

Gaddafi - who ruled Libya for four decades - was ousted and slain in October 2011 amid a NATO-backed uprising.

'People are getting their heads chopped off. They're being drowned. Right now it's far worse than ever [than it was] under Saddam Hussein or Gaddafi,' Trump said.

'I mean, look what happened. Libya is a catastrophe. Libya is a disaster. Iraq is a disaster. Syria is a disaster. The whole Middle East. It all blew up around Hillary Clinton and around Obama. It blew up.'

Calling Iraq the 'Harvard of terrorism,' Trump said the country had turned into a 'training ground for terrorists.'

'If you look at Iraq from years ago, I'm not saying he (Saddam) was a nice guy. He was a horrible guy but it's better than it is now,' Trump said.

He also said the United States should have taken Iraq's oil, saying it was now being bought by China, and also going to Iran and the Islamic State group.

'They have plenty of money because they took the oil because we were stupid,' he said of ISIS. 'I said take the oil when we leave.'

Trump said his foreign policy strategy would be centered around beefing up the US military.

'All I know is this: we're living in Medieval times ... We're living in an unbelievably dangerous and horrible world,' he said.

'The Trump doctrine is simple,' he added. 'It's strength. It's strength. Nobody is going to mess with us. Our military will be made stronger.'

Trump on Sunday also went after his Republican rival Ben Carson, who has surged past him in the closely watched, early-voting state of Iowa.

According to a Bloomberg/Des Moines Register poll out Friday, Carson claims 28 percent support from likely voters in the Republican Iowa caucus, compared to 19 percent for Trump.

It was the second poll in two days that had Carson knocking Trump off his perch in Iowa, an intensely fought-over state because it votes first in the lengthy US nominating contests.

'Ben Carson has never created a job in his life (well, maybe a nurse)' Trump tweeted about his main GOP rival - but he added 'I get along with everybody'

'Ben Carson has never created a job in his life (well, maybe a nurse),' Trump tweeted of the retired pediatric neurosurgeon, a fellow political newcomer.

'I have created tens of thousands of jobs, it's what I do.'

But Carson, who has cemented his support among Christian evangelicals, shrugged off Trump's darts in an interview with Fox News Sunday, saying, 'I refuse to get into the mud pit.'

'He is who he is. I don't think that's going to change. And I am who I am. That's not going to change either,' he said of Trump.

In his interview with CNN, Trump acknowledged he was 'surprised' by Carson's advance, calling an Iowa event he was at several days ago a 'love fest.'

'I like Ben but he cannot do with trade like I do with trade. He can't do a lot of things like I do,' Trump said, adding that Carson was also 'very, very weak on immigration' and a 'low energy person.'

Presidential hopeful Ben Carson, pictured October 9, has overtaken rival Donald Trump in polling among likely Republican voters in the early battleground state of Iowa

A new CBS News 2016 'Battleground Tracker' poll out Sunday showed Trump and Carson tied in Iowa at 27 percent, with Trump holding onto double digit leads over the doctor in South Carolina and New Hampshire.

The poll was based on 3,952 interviews done October 15-22, with the margins of error varying per state - 6.5 percent in Iowa, 6.6 percent in New Hampshire and 5.3 percent in South Carolina.

Alleging that President Barack Obama has 'divided this country,' Trump said that, in contrast, he would bring about bipartisanship.