US presidential candidate Donald Trump has expressed 'regret' for sometimes saying the 'wrong thing' on the campaign trail.

"I've never wanted to learn the language of the insiders, and I've never been politically correct - it takes far too much time", he told a rally in North Carolina.

But he followed this with: "Sometimes in the heat of debate and speaking on a multitude of issues, you don't choose the right words or you say the wrong thing.

"I have done that. And, believe it or not, I regret it, and I do regret it. Particularly where it may have caused personal pain.

"Too much is at stake for us to be consumed with these issues - but one thing I can promise you this: I will always tell you the truth.

"While sometimes I can be too honest, Hillary Clinton is the exact opposite - she never tells the truth," he added.

His change of tactics comes after several apparent slip-ups in recent months.

Most recently, Mr Trump has been criticised for seeming to suggest that those who hold guns in the US could do something about rival Hillary Clinton.

He told a North Carolina rally: "If (Mrs Clinton) gets to pick her judges, nothing you can do, folks. Although the Second Amendment people - maybe there is, I don't know."

He also accused President Barack Obama of founding the terror group ISIS, but took to Twitter to say that his words were being misinterpreted by the media.

His mea culpa comes amid another shake-up in his presidential campaign - which is the second in less than two months.

The head of conservative news website Breitbart News, Steve Bannon, was this week appointed campaign chief executive officer, while senior adviser Kellyanne Conway was promoted to the post of campaign manager.

Mr Trump has been slipping in recent opinion polls compared to Mrs Clinton - but this has been disputed by special counsel at the Trump Organisation, Michael Cohen.