A staff shake up for Donald Trump as he sacks his controversial campaign manager Corey Lewandowski.

The presidential hopeful has made the cut under apparent pressure from his inner circle after a number of campaign setbacks and heavy criticism from Republicans.

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US correspondent Jack Tame told Rachel Smalley it could have something to do with the choice of states on Donald Trump's itinerary for the next part of the campaign.

"States like Utah that are Republican strongholds you think, why on earth would you waste time going to a state like Utah when the Republicans are likely to win there, surely you should be focusing on some bellwether states."

Lewandowski's departure comes as Trump has faced setbacks in the past two weeks.

His renewed calls to ban Muslims from entering the United States have drawn heavy criticism from Republicans, and seen corporate sponsors withhold funding.

But as CNN's Stephen Collinson said, the problems have more to do with Trump than Lewandowski.

"It remains to be seen if Donald Trump can change. You can make changes to the organisational structure of your campaign but, at the end of the day, it comes down to the candidate."

Collinson said Team Trump figured it had to make changes after recent polls have seen Trump trail Clinton. 

"I think this is a real sign the campaign realises it needs to retool, as it heads into the convention next month and the stretch run into the election in November."