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U.S. Secretary of State Hillary Rodham Clinton's handshake Thursday with the president of Burma may be the start of a new dialogue between the two nations, but one U.S. lawmaker is warning that the regime's "DNA remains fundamentally brutal."

In the first top-ranking visit by a U.S. official in more than 50 years, Clinton praised the next generation of leadership in Burma -- also known as Myanmar -- but tempered her enthusiasm by saying the country must expand political freedom and cut off its ties to North Korea.

"It is encouraging that political prisoners have been released, but over 1,000 are still not free," Clinton said during a visit to the presidential palace in the new capital of Naypyitaw.

Clinton added that the release of Nobel peace laureate Aung San Suu Kyi, who is now allowed to participate in politics after being under house arrest for most of the past 20 years, is a milestone, but freedoms must be extended to all political parties that wish to participate in the nation's political development.

"The United States is prepared to walk the path of reform with you if you keep moving in the right direction," Clinton said.

But some members of Congress and outside observers have expressed concern that the trip is an undeserved reward for the regime.

"I am concerned that the visit of the secretary of state sends the wrong signal to the Burmese military thugs," said Rep. Ileana Ros-Lehtinen, R-Fla., chairwoman of the House Foreign Affairs Committee. "Secretary Clinton's visit represents a monumental overture to an outlaw regime whose DNA remains fundamentally brutal."

"The United States is taking a gamble, but much of the outcome rests on its own insistence on human rights progress," Benjamin Zawacki, a specialist on the country for Amnesty International.

Indeed the new leadership is still far from legitimate. Thein Sein's ascension to the presidency is marred by claims his election last year was neither free nor fair. Amnesty notes that the country still mistreats ethnic minorities, and put in its new constitution immunity for past misdeeds by the ruling junta. T. Kumar, Asia and the Pacific advocacy director for Amnesty International USA, said leaders there know how to manipulate foreign advocates.

"There are over 1,500 political prisoners, including some in cells designed to hold dogs," Kumar said. "Abuses in ethnic minority areas are continuing, including rape. What is disturbing is that the regime in Myanmar seems to have taken for granted that the U.S. government has other priorities than promoting respect for human rights and freedoms in the country."

Still, the U.S. is trying to incentivize the new civilian government's movement toward a pro-democratic direction. The U.S. has given the go-ahead for Burma's participation in a U.S.-backed grouping of Mekong River countries. Clinton said the U.S. will no longer block enhanced cooperation between Burma and the International Monetary Fund, and will support intensified U.N. health, microfinance and counternarcotics programs.

Clinton also delivered a letter from President Obama.

"I have asked Secretary of State Clinton to visit your country to discuss your vision for reform, explore how the United States can support and advance your efforts to transition to democracy and promote protection of human rights, and talk directly to your government and citizens about prospects for enhancing relations between our two countries," Obama wrote. "There is much work to be done, and as Secretary of State Clinton and I have said previously, the United States stands ready to serve as a genuine partner in your effort to achieve lasting change."

To the extent that Burma is ready for change, Sein told Clinton that her visit is "a "historic milestone" that would "enhance relations and cooperation." According to a senior U.S. official, who spoke on condition of anonymity to The Associated Press, Sein also delivered a 45-minute presentation in which he acknowledged Burma's troubled history and asked for U.S. help in making the transition from military to full civilian rule.

Clinton replied that the U.S. was "encouraged by the steps that you and your government have taken to provide for your people," the official said.

U.S. officials concede that the U.S. is taking a risk with offering an opening to Burma, which has been under near-blanket economic sanctions that block almost all American commercial transactions with the country. But with China's regional dominance, the U.S. is moving to warm relations with Vietnam, Indonesia and other countries that fall inside China's sphere of influence.

But breaking Burma's ties to North Korea, and a mutual pursuit of nuclear weapons, is also high on the agenda.

"We support the government's stated determination to sever military ties with North Korea," Clinton said.

Sein promised to honor the U.N. sanctions against North Korea but said he wants friendly relations with the country to continue. He also told Clinton that Burma is weighing whether to sign a new agreement with the U.N. nuclear watchdog that would allow unfettered inspections of atomic sites in the country, the U.S. official said.

Burma's behavior toward North Korea --and its pursuit of nukes -- is a marker for Sen. Dick Lugar, R-Ind., ranking member of the Senate Foreign Relations Committee.

Before Clinton's trip this week, he warned that Burma's "sincerity" in its commitment to reforms "must be judged by whether the words are followed by actions."

"Missing from the long list of good intentions has been reference to the growing relationship between North Korea and Burma, and close cooperation between their two militaries," Lugar said in a statement. "An early goal of the tentative U.S. re-engagement with Burma should be full disclosure of the extent and intent of the developing Burmese nuclear program."

Even with Clinton's historic visit, the enthusiasm toward her arrival was muted within Burma Her arrival was overshadowed by the arrival Thursday of the prime minister of Belarus and his wife, to whom two large welcoming signs were erected at the airport and the road into the city. No such displays welcomed Clinton.

The Belarus prime minister also made the front page of Thursday's edition of the government-run New Light of Burma newspaper. Clinton's visit was mentioned in a two-paragraph story on page 2.

Still, some in Burma welcome the attention from the U.S.

"I watched the arrival of Ms. Clinton on Burma TV last night," 35-year-old taxi driver Thein Zaw said. "I am very happy that Ms. Clinton is visiting our country because America knows our small country, whether it is good or bad."

The Associated Press contributed to this story.