Donald Trump appealed to his pro-life supporter base on Tuesday when he repeated his promise to protect the lives of the unborn. 

Crowds of supporters at his Make America Great Again rally in El Paso, Texas, broke into rapturous applause as Trump told them he had asked Congress to 'immediately pass legislation prohibiting extreme late-term abortion'. 

'Millions of innocent beautiful babies are counting on us to protect them. And we will,' he said.

The US president laid into Virginia Governor Ralph Northam who found himself at the centre of a media storm last month after describing a hypothetical situation in which a mother and doctor might agree the late-term abortion of a severely deformed baby.  

The Democratic governor told the WTOP-FM radio station: '[Third trimester abortions are] done in cases where there may be severe deformities. There may be a fetus that's nonviable. So in this particular example, if a mother is in labor, I can tell you exactly what would happen.

'The infant would be delivered. The infant would be kept comfortable. The infant would be resuscitated, if that's what the mother and the family desired, and then a discussion would ensue between the physicians and the mother.'

Northam made the comments while defending Virginia Democratic delegate Kathy Tran's bill seeking to loosen restrictions on late-term abortions. 

Asked in the legislature if her bill would allow abortion up to the moment of birth where the mother was 'dilating', she answered: 'My bill would allow that, yes.'

Trump told the El Paso rally that Northam's position amounted to supporting the 'execution' of babies. 

'But the governor stated that he would even allow a newborn baby to come out into the world and wrap the baby and make the baby comfortable and then talk to the mother and talk to the father and then execute the baby,' he told the jeering crowd. 

'Execute the baby ... incredible,' he added. 

His comments were welcomed by pro-life group the Susan B. Anthony List, which tweeted, 'Thank you, @POTUS for standing strong for LIFE!'

Trump made a similar pledge in his State of the Union address last month during which he attacked New York state's recently passed bill allowing abortion up to the moment of birth in some circumstances. 

'There could be no greater contrast to the beautiful image of a mother holding her infant child than the chilling displays our nation saw in recent days,' Trump said.

'Lawmakers in New York cheered with delight upon the passage of legislation that would allow a baby to be ripped from the mother's womb moments before birth.

'These are living, feeling, beautiful, babies who will never get the chance to share their love and dreams with the world.'

He added: 'I am asking Congress to pass legislation to prohibit the late-term abortion of children who can feel pain in the mother's womb. Let us work together to build a culture that cherishes innocent life. And let us reaffirm a fundamental truth: all children – born and unborn – are made in the holy image of God.'