Washington: Heading into the next round of presidential nomination contests over the weekend, tough talking Republican front-runner Donald Trump made clear that he would not order the US military to violate international laws to fight terrorism.

Pundits were quick to see "an abrupt about-face" in the brash billionaire`s explanation who has tied the Republican establishment into knots with his statements advocating something "tougher than waterboarding" and going after the families of terrorists.

During Thursday night`s debate on Fox News, Trump reaffirmed his willingness to target the families of terrorists and supported the use of waterboarding.

"We should go for waterboarding and we should go tougher than waterboarding," he said and told the moderators that the military would indeed carry out his orders.

"They won`t refuse. They`re not going to refuse me. Believe me," Trump said.

Several former defence and intelligence officials had criticised his stand suggesting that Trump was advocating torture and killing of terrorists` families -- though he never said so -- and that military officials would not obey such illegal orders.

A group of more than 100 leaders in the Republican foreign policy and national security community even wrote an open letter Wednesday condemning Trump and pledging to oppose his presidential candidacy.

But in a statement on Friday, Trump said that he understands "that the United States is bound by laws and treaties" and that he would "not order our military or other officials to violate those laws and will seek their advice on such matters."

"I will not order a military officer to disobey the law. It is clear that as president, I will be bound by laws just like all Americans and I will meet those responsibilities," he added.

Katrina Pierson, a Trump spokesperson, said the candidate had been misunderstood.

"He realised they took him literally, that`s why he put out the statement," she told CNN. "What he`s saying is that he wants to go after them with the full force of everything we have."

Meanwhile, with the Republic establishment ganging up against him, the Trump campaign announced that he will no longer speak at the Conservative Political Action Conference, the annual gathering of the who`s-who of the conservative world Saturday.

Trump will instead attend rallies in Kansas and Florida in a clear snub of the CPAC, described as a must-do event on the conservative calendar, with the other candidates and many of the former candidates making an appearance this year.

Trump`s snub came amid establishment`s efforts to bring him down with the 2012 Republican nominee Mitt Romney calling him a "phony and a fraud" and urging Republicans to vote for one of his opponents.

All three of the other candidates -- Texas senator Ted Cruz, Florida senator Marco Rubio and Ohio governor John Kasich -- said during Thursday night`s Republican debate they would back Trump if he were the eventual nominee.

But they have railed against him, with Rubio using the hashtag #NeverTrump on Twitter and calling him a "con artist" that would split up the Republican Party.

Meanwhile, Trump got some support from an unexpected quarter. Former Democratic presidential candidate Jim Webb said he won`t be voting for Clinton, but he hasn`t ruled out casting his ballot for Trump.

Webb, who briefly flirted with an independent bid before deciding against it, said on Friday morning that the Democratic front-runner wasn`t inspirational.

"I would not vote for Hillary Clinton," Webb told MSBNC.

When asked whether he`d vote for Trump, Webb said he wasn`t closed to the idea. "I`m not sure yet. I don`t know who I`m going to vote for," he said.