US President Barack Obama (L) and his Vietnamese counterpart Tran Dai Quang review an honour guard. (AFP Photo)
Barack Obama praised "strengthening ties" between the United States and Vietnam at the start of a landmark visit Monday, as the former wartime foes deepen trade links and share concerns over Chinese actions in disputed seas.
The visit to the dynamic and rapidly growing southeast Asian nation is Obama's first -- and the third by a sitting president since the end of hostilities in 1975.
"We come here as a symbol of the strengthening ties we have made over the last several decades," Obama told his counterpart President Tran Dai Quang in Hanoi during the first of a series of meetings with the communist nation's senior leadership.
The US leader said he hoped his three-day visit will demonstrate to the Vietnamese people "the warmth and friendship" that exists between the two countries.
The nations have experienced an astonishing turnaround in their relations from bitter foes physically and psychologically scarred by a decade of war, to regional allies.
In a symbol of that shift, the two leaders shook hands ahead of the meeting in a room dominated by a large bust of Vietnam's communist revolutionary hero and US nemesis Ho Chi Minh.
Earlier as Obama's motorcade swept through the city Monday morning, thousands of bystanders lined Hanoi's streets, many holding smartphones aloft.
"I like Obama as he seems moderate," Nguyen Toan Thang, an office worker, told AFP. "This is a once in a lifetime chance to see the US president coming to Vietnam."
Obama will also hold talks with Prime Minister Nguyen Xuan Phuc.
But the most important one-to-one will be with de facto leader Nguyen Phu Trong, the general secretary of the Communist Party, later in the afternoon.
Trong and Obama met last July, when he was given a prestigious Oval Office meeting.
'Look towards the future'Trade will dominate during the trip, with Obama keen to make the case for a trans-Pacific trade deal to reduce tariffs that faces an uncertain future.
On Tuesday afternoon Obama will fly to Ho Chi Minh City, the southern Vietnamese metropolis formerly known as Saigon, which is the country's thriving commercial heart four decades after American troops beat a hasty retreat.
There he will meet with tech entrepreneurs and hold one of his trademark town hall gatherings with young people.
The State Department said both countries had announced a partnership to help tackle climate change in Vietnam, a country particularly vulnerable to flooding and creeping salinisation.
The visit comes at a time when America has rarely, if ever, been so popular among ordinary Vietnamese.
A poll last year by the Pew Research Centre found 78 percent of Vietnamese have a favourable view of the US, the third highest in Asia after the Philippines and South Korea.
The approval rate was even higher among young people, a huge demographic in nation where the median age is around 29.
Like most Vietnamese, 25-year-old Doan Quang Vinh from Hanoi was born long after the war.
"For me, the American war against Vietnam is a matter of the past, and though we must not forget the past, we should not dwell on it. We should look towards the future," he told AFP.