Protestant pastors in the US mainly say they approve of the job President Donald Trump is doing, according to a study by LifeWay Research.

The study found 51 per cent of senior pastors approve of Trump's performance, with 25 per cent strongly approving.

'After almost two years of actions and statements from the White House, most pastors likely consider some positive and others negative,' said Scott McConnell, executive director of LifeWay Research.'When asked to evaluate the president's job performance with no neutral option, most pastors approve.'

However, nearly three in 10 (28 per cent) disapprove and another 20 per cent say they aren't sure.

McConnell said that many were reluctant to give an opinion.

'Compared to the middle of President Obama's first term, we see twice as many pastors say they're undecided on President Trump's job performance,' he said.

LifeWay compared the findings with a poll before the 2010 midterm elections, which found 30 per cent of pastors approved of President Obama's job performance, with 61 per cent disapproving and only nine per cent saying they weren't sure.

'There is no lack of information on what President Trump is doing or how he is doing it,' said McConnell, 'so the undecided posture appears to be an unwillingness to identify with either of the political sides that have emerged in American politics.'

The hesitancy of pastors to take sides where Donald Trump is concerned stretches back to the presidential election.

Despite 52 per cent of Protestant pastors identifying as a Republican and only 18 percent calling themselves a Democrat in the LifeWay Research survey prior to the November 2016 election, only 32 per cent said they planned to vote for Trump. A full 40 per cent said they were undecided, with 19 percent planning to vote for Hillary Clinton.

African-American pastors are the least likely to approve of the president's handling of the job by a very wide margin. Only four per cent approve of his performance, while 85 per cent disapprove.

Slightly more than half of white pastors (54 per cent) approve, along with slightly less than half of pastors of other ethnicities (47 per cent).

'In 2016, only six per cent of African-American pastors identified as Republican,' said McConnell, 'and nothing in President Trump's first two years has generated approval from African-American pastors beyond that level.'

Younger pastors are the least likely age group to approve of Trump's performance. Four in 10 (41 per cent) of those 18 to 44 say he's done a good job, while 56 per cent of those 45 and older support President Trump's job performance.

Pentecostals (86 per cent) and Baptists (68 per cent) are most likely to approve of the president's performance.

Few Presbyterian/Reformed (28 per cent) and Methodists (25 per cent) say they support the job President Trump has done.

Among other findings, male pastors (56 per cent) are more likely to approve than female pastors (30 per cent) and self-identified evangelical pastors (63 per cent) are more likely to approve than self-identified mainline pastors (41 per cent).