As he gained the endorsement of the New England Police Benevolent Association on 10 December, Republican presidential candidate Donald Trump defended his call to temporarily ban Muslims from the US and pledged to punish police killers with death, if elected president. Trump made the comments to a crowd of law enforcement officers from Massachusetts and New Hampshire in the city of Portsmouth.

Trump provoked international uproar earlier this week by calling for Muslims to be blocked from entering the US after shootings in California by two people who authorities said were radicalised Islamists. Trump likened the outrage to comments over the summer that Mexico was sending rapists and other criminals into the US. He then said illegal border-crossers from Mexico were carrying "tremendous infectious disease".

"When I said illegal immigration all of a sudden people started thinking. And two weeks later, three weeks later, it was really a nice conversation. When I talked about what I said the other day, all of a sudden I'm watching the shows this morning, and I'm watching the shows tonight, 'Well you know Trump has a point. The visa system is not working'. This woman came in on a marriage visa and she was totally radicalised, and she came in and all of a sudden they're saying it's not working, the visa system, and then another show is talking about something else not working," Trump said.

"We're going to get down to brass tacks. You look at what happened – so many people, so many people knew that those two in California were up to no good. They saw bombs sitting on the floor. They had one guy who bought the guns. They had another person that said, 'oh I didn't want to report them because I didn't want to go racial profiling'. Oh OK, she sees pipe bombs sitting all over the place didn't want to racially profile. I mean how stupid do they think we are?" he added.

Trump called the organisation's endorsement a huge honour and promised to protect officers by using an executive order to give the death penalty to police killers.

"One of the first things I do in terms of executive order if I win will be to sign a strong, strong statement that will go out to the country, out to the world, that anybody killing a policeman, policewoman, police officer. Anybody killing a police officer: death penalty. It's going to happen. OK? We can't go. We can't let this go," Trump said.

A Reuters/Ipsos poll conducted this week, which includes responses from before and after Trump made his proposal on 7 December, shows he still holds a commanding lead in the Republican race.