Republican presidential nominee Donald Trump has for the first time said he is open to softening his hardline stance on immigration, as he seeks to appeal to more moderate and minority voters after his poor showing at the latest opinion polls.

When asked during a town hall event aired on Tuesday night on Fox News if he would change the law to accommodate people who contribute to society, have been law-abiding and have children in the United States, Mr Trump said: "There certainly can be softening because we are not looking to hurt people.

"We want people, we have some great people in this country."

This is a notable change from his earlier position of establishing a "deportation force" which will expel all 11 million illegal immigrants in the US - a policy that won the support of his base, but was unpopular with Hispanic voters in key states such as Florida.

The Trump campaign has since used another tactic to appeal to moderates, by highlighting that deportation was something previous presidents, including President Barack Obama, had done.

"Now, we can be more aggressive than them, but we want to follow the laws," said Mr Trump, who steered clear of the word "deportation" during the hour-long town hall event.

Flanked by mothers who had lost their children to crimes committed by illegal immigrants, Mr Trump assured the audience in San Antonio, Texas: "We can stop it, we have to stop it."

"We have some really bad gang members and horrible people, those people are going out Day One," he added.

However, Mr Trump is not backing down on some of his signature immigration policies, including building a wall along the US-Mexico border.

Defiant in the face of critics who say he will not be able to achieve it, he said he is "100 per cent" certain that he will build the wall and "it gets higher and higher and higher every time someone says we are not going to do it".

Mr Trump had been scheduled to deliver a speech on immigration in Colorado today, but it was postponed, possibly till next week.

There had been much talk about his immigration stance over the weekend, especially after US media reported that he had held a meeting with his newly formed Hispanic advisory panel on the matter.

On Sunday, Mr Trump's new campaign manager Kellyanne Conway also said his immigration plans were "to be decided".

Early yesterday morning, Ms Conway told CNN that Mr Trump was "looking at the mechanism, looking at the policy" to make sure his immigration plan is carried out "humanely and fairly as he knows there are people involved here".

Experts suggest that Mr Trump is trying to broaden his appeal as Democratic presidential nominee Hillary Clinton climbs in national polls.

According to the most recent poll by NBC News and SurveyMonkey, Mrs Clinton has an eight-point advantage over Mr Trump.

She also has an overwhelming lead when it comes to minority voters, with 73 per cent of Hispanic voters supporting her and only 22 per cent supporting Mr Trump.