SIEM REAP, Cambodia  - US Secretary of State Hillary Clinton held landmark talks Friday with Myanmar President Thein Sein as he pleaded for the global community to end decades of isolation for his nation.
The pair met in the Cambodian tourist town Siem Reap on the sidelines of a major US business conference, after the US on Wednesday gave the green light to firms to invest in Myanmar, including in oil and gas.
Shaking hands in the lush gardens of a luxury hotel, Clinton told Thein Sein that she was sending "a very distinguished delegation" to his country to scout out opportunities for US business and investment.
Thein Sein later told a dinner attended by top US business leaders that his impoverished Southeast Asian nation would welcome an influx of investment into a country which had "lagged behind in development for the past 60 years".
"Myanmar is at a critical juncture, where she has evolved from the military administration putting an end to armed conflict to achieve sustainable peace and moving toward a new democratic era," Thein Sein said.
Among the 200 companies represented at the largest ever gathering of American businesses in Southeast Asia were Coca-Cola, Caterpillar, Goldman Sachs, Ford and General Electric.
They are all keen to move into Myanmar seen as virgin territory for the United States after so many decades of isolation.
It was Clinton's second meeting with Thein Sein after she became the first US secretary of state to visit Myanmar in half a century during a trip to the country last year.
Washington has been surprised by the speed of reforms which have taken hold in the long military-dominated nation, leading to the freeing from house arrest of democracy icon Aung San Suu Kyi and her subsequent election to parliament.
The decision to ease the sanctions will please US firms eager not to miss out on what some economists expect to be a gold rush in the resource-rich nation.
But Washington has faced criticism from rights groups concerned it is moving too fast in its eagerness to cash in on Myanmar's vast business potential.
Asian firms have been doing business in Myanmar for years, while the European Union suspended most of its sanctions against the country in April.
Clinton told Thein Sein that the US wanted to encourage further reforms, which has impressed the West with its release of hundreds of political prisoners and by welcoming Suu Kyi and her party into mainstream politics.
"We want to help you keep going. We are very committed," she said.
Thein Sein hailed the US decision to ease its investment embargoes.
"I am very pleased to see our bilateral relationship improving dramatically," said the Myanmar leader, a former general who shed his army uniform when he took power as the head of a quasi-civilian government last year.
The meeting, which lasted about an hour, raised a host of issues including political prisoners, environmental protections and the plight of the country's stateless Muslim Rohingya, officials said.
"They were talking seriously about how to take the country forward on its reform goals, on its investment goals," a senior State department official said.
In a speech earlier on Friday Clinton acknowledged that as Myanmar opens up "there will be a lot of challenges" but said she hoped to see "continuing progress there".
Washington was setting up "protections to ensure that increased American investment advances the reform process" she said, because US firms will have to report on transparency and labour rights.
Myanmar - along with regional neighbours - has called for all sanctions to be lifted as the country embarks on its "second wave" of economic reforms.
Suu Kyi welcomed the sanctions decision, but called for greater transparency at state-owned Myanma Oil and Gas Enterprise, which US firms will be able to do business with under the new rules.
Human Rights Watch however said Washington had "caved to industry pressure" because it did not insist on reforms in governance and human rights.