UN Secretary General Ban Ki-moon in Burma visit
United Nations Secretary General Ban Ki-moon is meeting senior officials and addressing a joint session of parliament in Burma - the first foreigner to do so.
Mr Ban, on a three-day visit to Burma, said he felt "optimistic" but warned of "hard work ahead", especially in the peace process with ethnic minorities.
He met President Thein Sein and is to meet opposition head Aung San Suu Kyi.
Mr Ban last visited Burma in 2009, but was then denied access to Ms Suu Kyi.
This trip is the latest high-profile diplomatic visit to the once-isolated nation since a reformist government took office a year ago.
''I am looking forward to my meetings and feel much more optimistic,'' he said.
Mr Ban left frustrated after his last visit on the invitation of former junta strongman General Than Shwe, describing it as a "very difficult mission".
On Tuesday he will meet Ms Suu Kyi, who led her pro-democracy party to win 43 seats in by-elections on 1 April. She was in detention during his last visit but was released 15 months later.
More needs to be done in the process of reforms, Mr Ban said, particularly in achieving lasting peace with ethnic minorities.
The resurgence of fighting between the Burmese army and Kachin rebels has displaced tens of thousands of people, says the BBC's Rachel Harvey, who is travelling with Mr Ban in Burma. But the UN has struggled to get the access it needs to be able to help them.
Mr Ban is also due to visit the northern Shan State, one of the world's biggest opium-growing regions, where the UN has started a poppy eradication programme.
On Sunday, he also paid his respects at the tomb of the late Burmese diplomat U Thant, who was UN secretary general from 1961 to 1971.High level visits
The current UN chief's visit to Burma is the latest in a series of high-level visits by foreign leaders and diplomats in the past year, following a series of reforms aimed at encouraging Western nations to lift sanctions.
European Union foreign policy chief Catherine Ashton announced in Burma on Saturday that the EU would open an embassy-level office in the country.
Earlier this week, it suspended non-military sanctions against Burma for a year in recognition of "historic changes".
Ms Ashton said the new office in Rangoon would offer investment and expertise, and oversee the management of aid programmes, particularly in remote rural areas.
EU diplomats have said that the new office in Rangoon will also have a political role.
Referring to the number of high-level visits to Burma, Mr Ban said the recent rush should be translated into concrete action.
Right now it is positive, he said, but pledges of support will need to be coordinated, adding that in his view the UN is best placed to fulfil that role