U.S. President-elect Donald Trump will not pursue investigations against Hillary Clinton over her family's charity or her use of a private email server while she was secretary of state, MSNBC said, dropping a threat made to his Democratic rival during the bitter presidential campaign.

Republican Trump had vowed to jail Clinton and crowds at his rallies chanted "Lock her up." But he now believes she "has been through enough”.

During the campaign, opinion polls found that many U.S. citizens did not find Clinton trustworthy.

The FBI investigated Clinton's use of a private email server while she was secretary of state during President Barack Obama's first term, concluding in July that her actions were careless but that there were no grounds for bringing charges.

If Trump does abandon his vow to appoint a special prosecutor for Clinton it will be a reversal of a position he mentioned almost daily on the campaign trail, when he dubbed her "Crooked Hillary."