Speaking outside the White House in Washington, DC, Mr Turnbull repeatedly dodged questions about whether he wanted Mr Joyce to remain as the Nationals leader.

“Barnaby Joyce is the leader of the National Party of Australia. As leader of the National Party of Australia in a Coalition government, he is my deputy prime minister,” Mr Turnbull told reporters.

“The leadership of the National Party is a matter for the National Party and I’ve been at great pains to stress that I have not, nor has my party, sought to influence in any way the deliberations of the National Party, any more than I’d expect the National Party to seek to influence deliberations of the Liberal Party.”

MORE: Questions of Joyce’s 3000km road trip

Mr Joyce’s leadership is under attack after it was revealed that he was expecting a child with his former staffer Vikki Campion.

His Nationals colleague, Victorian MP Andrew Broad, says he will move a resolution to oust Mr Joyce as party leader on Monday.

He told ABC radio Mr Joyce should also quit as minister and go to the backbench “to clear his head” and to “regain his credibility”.

AUSTRALIA PROVIDES ‘POWERFUL DEMONSTRATION’ ON GUNS

As the US reels from another mass shooting in a high school, many are looking to Australia’s example on the gun restrictions enacted after the Port Arthur Massacre of 1996.

It is not clear whether Mr Turnbull will discuss Australia’s gun laws when he meets with US President Donald Trump in the White House on Friday, but the Prime Minister indicated that he did not want to lecture the Americans on the issue.

“It’s not for me to get involved in a contentious domestic political debate here, but Australia’s experience in gun law reform, undertaken so courageously and effectively by John Howard more than 20 years ago, is a very powerful demonstration of the success of our policies,” he said.

100 YEARS OF MATESHIP

Mr Turnbull’s first day of engagements in Washington, DC, highlighted the close military links between Australia and the US.

“It’s 100 years since Sir John Monash led Australian and American troops into battle, and ever since then Australians and Americans have fought side by side to defend our freedoms, to defend our shared values,” Mr Turnbull said.

“Every meeting I have on this visit — including of course with the President tomorrow — will be reminded of and celebrate that 100 years of mateship, which has given us 100 years of security and prosperity, but it will also set the course for the next 100 years of partnership, of mateship, of the commitment that Australia and America have to each other.”

Overnight, the Prime Minister met with Treasury secretary Steve Mnuchin, Homeland Security secretary Kirstjen Nielsen, National Security Agency director Mike Rogers, and he will pay tribute to fallen soldiers with his wife Lucy later today at the war cemetery in Arlington.

Mr Turnbull is leading a delegation of Australian premiers, chief ministers and business executives with the aim of strengthening economic ties with the US.

Mr Turnbull said the US was Australia’s most important strategic and economic partner, a theme he will highlight during a speech at Saturday’s National Governors Association meeting.

“One of the priorities that we have here … is to ensure that our engagement is broader and deeper and goes beyond Washington, New York and Los Angeles and reaches into every part of the United States to create more opportunities for Australian investment and partnership in America,” he said.

“This is an opportunity to broaden and deepen that engagement … It means more investment and more jobs.”