American Vice-President Mike Pence has been welcomed by Prime Minister Malcolm Turnbull, who hailed his visit as a reflection of the importance the Trump government placed on relations with Australia.
The Vice-President arrived at Kirribilli House about 9am in an armoured black Cadillac bearing the American licence plate "800 002" and with a heavy security detail that included suited agents, uniformed soldiers and circling helicopters.
Security was tight for Mr Pence and his entourage, with a large police contingent patrolling the streets while police helicopters hovered overhead.
Sydney's famous Harbour Bridge was closed so Mr Pence's motorcade could make the short trip from his luxury hotel in the CBD to Kirribilli.
Mr Pence was officially greeted by the Governor-General Peter Cosgrove at Admiralty House on the Kirribilli foreshore, before holding talks with Mr Turnbull.
Mr Pence's visit has been viewed by many as a chance to smooth over the Australian-American relationship, following a stern phone call between the two leaders in February.
Mr Trump was reported to have chastised Mr Turnbull for what he described as his worst phone call with a world leader that day and was reported to have ended the planned one-hour chat more than 30 minutes early.
Mr Turnbull opened the talks with Mr Pence with a reference to Australia and America's long history of military alliance, one the PM noted stretched back more than a century to World War I before formal alliances were brokered 60 years ago.
"We are very honoured you are visiting us here so early in the term of new Trump administration," he said. "It is the earliest visit by a Vice-President in a term of a new administration in history."
"Australia has stood shoulder to shoulder with the United States in every major conflict in the past 99 years."
Mr Pence reassured the PM that all is well between the US and Australia.
"I bring greetings this morning from president of the United States. I spoke with him first thing and he wanted me to pass along his very best regards," Mr Pence said.
"The president wanted me to be here early in this administration to reaffirm this strong, historic alliance between the United States of America and Australia.
"My presence here today at the president's direction is about a reaffirmation of the strong ties in both our security and our prosperity."
Watched on by Australia's ambassador to the US and the acting US Ambassador to Australia, Charge d A'ffaires James Carouso, Sir Peter Cosgrove told Mr Pence how the relationship can be traced back to the battlefields of World War I in France when General John Monash had two US regiments under his command at the battle of Hamel.
"The relationship between our two nations is as strong today as it has been since the first time we saw each other on the battlefield," the Governor-General said.
Earlier Mr Pence, his wife Karen and their daughters Charlotte and Audrey joined Mr Turnbull, wife Lucy, daughter Daisy and son-in-law James Brown, and their baby daughter Alice, for a relaxed morning tea at neighbouring Kirribilli House on Sydney Harbour.
Mr Pence said his wife had enjoyed spending time with Mr Turnbull's grandchildren.
"My wife was extremely impressed with your grandchildren, we don't have any yet," he said.
Security issues and East Asian geopolitics are expected to feature high on the agenda for talks.
The pair will hold a press conference at noon, and will then be joined by senior government ministers and business leaders including Qantas boss Alan Joyce for a lunch in the gardens of Admiralty House.
Mr Pence will end his day of official engagements by meeting Opposition Leader Bill Shorten and business leaders in the city.
with AAP
