Aung San Suu Kyi will receive the US Congress' highest honor on Wednesday during a landmark trip in which she has called for the lifting of sanctions on her native Myanmar.

US Secretary of State Hillary Clinton meets Myanmar opposition leader Aung San Suu Kyi at the State Department in Washington on Tuesday. Gary Cameron / Reuters

The Nobel peace laureate was awarded the Congressional Gold Medal in 2008, during the 15 years she spent under house arrest, and is only able to receive it now as relations thaw between the United States and the South Asian nation.

On Tuesday Suu Kyi thanked the US for its years of support but said further reforms must proceed without the pressure of sanctions and insisted improved relations with Washington would not pose a threat to Beijing.

"In the end, we have to build our own democracy," she said in a speech in which she appeared careful not to annoy leaders back home who have initiated reforms.

The opposition leader had long supported economic sanctions to pressure her jailers, Myanmar's junta, which nominally disbanded last year.

Washington has been rolling back restrictions, in July opening Myanmar up to US investment despite Suu Kyi's earlier unease about US firms doing business with the state-owned oil and gas company.

"There are very many other ways in which the US can help us to achieve our democratic ends ... Sanctions are not the only way," she said.

Suu Kyi, now a member of parliament, said she believes President Thein Sein is "keen" on change in the nation but said the judiciary - and not the executive - was reform's "weakest arm".

"We have passed a first hurdle, but there are many more hurdles to cross," she said.

While acknowledging it was a "natural question" whether US interest in Myanmar was spawned by a desire to contain China, Suu Kyi said the warming ties should not "in any way be seen as a hostile step towards China".

"For us to put it very simply, it would be to our advantage for the United States and China to establish friendly relations. This would help us a great deal," she said.

Suu Kyi, dressed in a red jacket with three small pink flowers in her hair, began her visit by meeting another of the world's most prominent women, US Secretary of State Hillary Clinton, who marveled at her political odyssey.

"It's wonderful to see Suu Kyi back in Washington as a free and forceful leader of a country opening up to the world in ways that would have been difficult to imagine even recently," Clinton said.

But Clinton warned that Myanmar still had "a lot of work" to do.

"The government and the opposition need to continue to work together to unite the country, heal the wounds of the past and carry the reforms forward," said Clinton, who paid a landmark visit to Myanmar in December.

She mentioned the need to "guard against backsliding, because there are forces that would take the country in the wrong direction if given the chance".

Suu Kyi said that her party, the National League for Democracy, wanted to "help the government in any way possible to bring about peace and harmony".

"We are not in a position to decide what we do and how we operate because we are not the government. I think this has to be understood by those who wish the NLD to do more," she said.

Agence France-Presse