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

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 United States 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.

The United States 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 United States 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 formerly known as Burma 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.

On the eve of Suu Kyi's trip, her party said that authorities freed another 87 political prisoners in what analysts saw as a new gesture by Thein Sein ahead of his own visit to the United States next week.

In the award ceremony before the Asia Society and US Institute of Peace, Suu Kyi took pains to reassure China, which was the junta's main ally.

Many US observers believe Thein Sein launched the reforms out of concern over Beijing's overwhelming political and economic dominance in Myanmar.

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, 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, including freeing remaining political prisoners and ending alleged military contacts with North Korea.

"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.

"That is also key to guard against backsliding, because there are forces that would take the country in the wrong direction if given the chance," she said.

Clinton also called for Myanmar to address tensions in Rakhine state, where recent violence between majority Buddhists and the Muslim Rohingya minority left scores dead and displaced tens of thousands of people.

Suu Kyi, who is widely respected in Washington, has come in for rare criticism from human rights activists, who have pressed for her to speak out on behalf of the 800,000-strong Rohingya population, whom Myanmar's government does not consider citizens.

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," but defended her record.

"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.

Asked separately about the Rohingya in an interview with Washington-based Radio Free Asia, Suu Kyi said that the key was to "remove the roots of hatred."

"You have to address these issues that make people insecure and that make people threatened," she told the broadcaster's Burmese service.