Opposition leader Aung San Suu Kyi says she is confident about prospects for democratic reforms in Myanmar after talks with the US Secretary of State Hillary Clinton.
Mrs Clinton held talks with the Nobel laureate at the lakeside mansion in Rangoon where Ms Suu Kyi has spent most of the past two decades as a prisoner in her own home.
Describing it as an historic moment for both countries, Ms Suu Kyi said more needed to be done by the new military-backed regime - but that engaging with it is a risk worth taking.
Mrs Clinton was on the final day of an historic three-day visit to Myanmar, also known as Burma.
Earlier, she delivered a personal letter from President Barack Obama to government leader President Thein Sein, offering a new phase in relations in return for democratic reforms.
Mrs Clinton says she held candid, productive talks with Mr Sein and other senior officials in Myanmar, as well as with Ms Suu Kyi.
The Secretary of State says Washington will encourage the tentative reforms by backing more aid and possibly sending an ambassador there.
Mrs Clinton says she made it clear that while the measures already taken may be unprecedented and welcome, they are just the beginning.
Myanmar's new government has surprised many with a series of changes, including freeing some political prisoners and easing some media restrictions.
The US is still assessing how sincere the new government is in its political and economic reform drive.
A BBC correspondent says Western nations are scrambling to find a response that will encourage the momentum of reform without rewarding too generously, too soon, the generals who run the country.