U.N. chief Ban Ki-moon made a landmark visit to a fast-changing Myanmar on Sunday to encourage further reforms and push for a further easing of Western sanctions to help normalise United Nations operations in the long isolated country.

Ban's trip was his first since a reformist, quasi-civilian government took office a year ago, ending five decades of authoritarian military rule and thawing Myanmar's relations with the international community.

The government, led by remnants of the former junta, has stunned the world with economic reforms and unprecedented engagement with the West, the political opposition and ethnic minority rebel groups.

Ban called that progress encouraging, but still tenuous. "I'm much more optimistic and hopeful about Myanmar," he told reporters in the remote capital Naypyitaw, where he was due to meet President Thein Sein and other important reformers.

"Nobody said this was an easy process. This process is risky and fragile. We can't always be unconditionally optimistic, we have to be mindful of this and have to nurture this process."

During his three-day visit, Ban will see a Myanmar that has undergone eye-opening changes since his last trip in July 2009 on the invitation of then-junta strongman Than Shwe, which he described as a "very difficult mission".

Since Than Shwe stepped aside on March 30 last year, four months after an election seen as rigged, the Southeast Asian country's former fourth-in-command Thein Sein has taken over and brought long-detained opposition leader Aung San Suu Kyi into the political fold.

FACELIFT
His government has started overhauling the tattered economy, easing media censorship, legalising trade unions and protests, freeing political prisoners and agreeing ceasefires with a dozen ethnic rebel armies.

Ban was to hold talks on Monday with Thein Sein and other ex-generals who were part of Than Shwe's inner circle and whom Ban described as 'key drivers' behind the political facelift that has prompted an easing of some sanctions this month by the European Union, United States, Australia and Canada.

He said he would discuss ways for Burmese businesses to engage with reputable Western firms to encourage responsible practices and boost investment. With sanctions softening, Ban said he could now push to deepen the U.N.'s work in Myanmar.

"U.N. activities have been restricted severely so I'm going to normalize U.N. development activities soon," he said. "I'll discuss with member states ... to authorise us to engage in full, normal operations."

Ban will travel on Monday to Shan state, one of the world's biggest opium-growing regions, to assess Myanmar's move to eradicate poppy cultivation by 2014. He is due to sign an agreement for U.N. support in compiling the country's first census since 1983.

Ban is also scheduled to give an address to Myanmar's huge new parliament on Monday, the first by a foreign dignitary.

He said he would raise the need to further relax the West's punitive measures 'to help Myanmar accelerate their focus and give some political incentives'.

Nobel laureate Suu Kyi's party was due to make its debut in the parliament last week after an historic April 1 by-election win, but has refused to take its seats because of a potentially protracted dispute over the wording of a swearing-in oath.

The ruling, army-backed party says it will not support her demand to change it. Ban said the issue was sensitive and called for all sides to act rationally.

"There's a general push from both sides to treat this issue with wisdom, without making it confrontational. I'm hopeful all sides will adopt flexible and constructive positions."