YANGON (AFP) - US President Barack Obama offered Myanmar a new era in relations if it reforms and promised democracy icon Aung San Suu Kyi his eternal support in letters hand-delivered by his top diplomat Thursday. The high-stakes personal intervention in a country long regarded by the West as a pariah state came during a historic visit by Hillary Clinton, the first US secretary of state to set foot in the isolated nation for 50 years. In a message to President Thein Sein, Obama offered a "new phase" in ties and requested "tangible outcomes" from a political reform effort which Washington is testing before deciding its next step. In his letter to Suu Kyi, Obama said that he had long admired the opposition leader's "brave and unwavering struggle for democracy". He wrote: "Thank you for the inspiration you provide all of us around the world who share the values of democracy, human rights and justice. We stand by you now and always." The country formerly known as Burma has surprised observers with a series of reformist moves in the past year including releasing Suu Kyi -- whom Clinton met Thursday for a private dinner in the main city Yangon -- holding dialogue with the opposition and freeing some political prisoners. Obama told Thein Sein, a former general, that Washington wanted to "explore how the United States can support and advance your efforts to transition to democracy and promote protection of human rights". US officials said the message, released by Clinton's aides, aimed to signal that Obama was ready to invest personal prestige in engaging Myanmar. The letter did not mention the words "Myanmar" or "Burma", thereby bypassing the controversy over the impoverished Southeast Asian state's true name. The former military junta renamed the country Myanmar in 1989 but the United States still uses Burma, in a practice intended to irk the generals, who ceded to a nominally civilian government this year. In her landmark talks, Clinton won promises of further reforms from Thein Sein and offered cautious incentives to encourage new action, saying more needed to be done before US sanctions could be lifted. "Any steps that the government takes will be carefully considered and... will be matched because we want to see political and economic reform take hold," she told reporters in Myanmar's isolated showcase capital Naypyidaw. Thein Sein, who took charge in March after Myanmar nominally ended decades of military rule, himself hailed a "new chapter in relations" as he met Clinton at his imposing palace decked out with chandeliers and gold-leaf chairs. Clinton said the United States would open talks with Myanmar to start joint searches for the remains of troops killed in World War II, when the strategically placed country was a major battleground. She also invited Myanmar to join as an observer the Lower Mekong Initiative, a US programme that offers cooperation on health and the environment in Southeast Asian nations, and voiced support for IMF missions to the country. "These are incremental steps and we are prepared to go further if reforms maintain momentum.