Media playback is unsupported on your device Media caption Aung San Suu Kyi said she trusted the Burmese president

Burma's opposition leader Aung San Suu Kyi says she believes Burma will hold democratic elections "in my lifetime".

In an exclusive interview with the BBC, she said she did not know when that would be or whether she would run.

She said political prisoners must be freed. Officials deny their existence.

Later in the day Ms Suu Kyi met William Hague - the first UK foreign secretary to visit Burma since 1955. He is one of several top foreign officials to have visited since elections in 2010.

The polls, which were the first in 20 years, elected a nominally civilian government to end military rule, although the military maintains a significant grip on power.

Ms Suu Kyi, 66, told BBC World News that she foresaw "a full democratic election in my lifetime", adding: "But then of course I don't know how long I'm going to live. But if I live a normal lifespan, yes."

Last month she formally registered her National League for Democracy (NLD) as a political party, after boycotting the 2010 polls because of electoral laws that prevented her taking part. The authorities officially approved the NLD registration on Thursday.

Of President Thein Sein, a former top general who stepped down to contest elections as a civilian, Ms Suu Kyi said: "I trust the president, but I can't yet trust the government for the simple reason that I don't yet know all the members of government."

Analysis William Hague came to Burma to encourage the government to continue on the path of reform. But he seems to have come away from his meetings having himself been encouraged. Mr Hague made clear that if the recent trend continued there could be rewards, including the lifting of sanctions. But he said this would only happen when there was a "complete process of reform". There is now a widely held view that Burma stands at a crossroads and the next year could prove critical in determining the scope and speed of change. In her interview with the BBC, Aung San Suu Kyi said things were not moving as quickly as many would like, but she added that she trusted President Thein Sein and believed him to be an honest man. That view will undoubtedly influence the thinking of western nations - Britain, the US and the EU in particular - who tend to take their cue from Burma's most famous former political detainee. Investors eye resourceful Burma

She added: "The most important thing about the president is that he is an honest man... He is a man capable of taking risks if he thinks they are worthwhile."

Asked whether the day was coming when she would run for that office, however, she replied: "I can't even tell whether this is something that I would like to do or would do."

Prisoner account

William Hague said after meeting his counterpart Wunna Maung Lwi in Nay Pyi Taw that "the foreign minister has reaffirmed commitments that have been made to release political prisoners".

"He said the changes are irreversible and I welcome that way of thinking," Mr Hague added.

"I stressed that the world will judge the government by its actions."

But in an interview with the BBC Burmese service later, Wunna Maung Lwi said Burma did not acknowledge there were political prisoners.

They are all criminals, he said, and it was up to the president to decide when prisoners were released - adding that prisoners had already been freed on three recent occasions.

Media playback is unsupported on your device Media caption Soe Win Than of the BBC's Burmese Service on his visit to the country's 'eerie' new capital

The government, he said, was focused on the development of the whole country.

Between 600 and 1,000 journalists, dissidents and monks who led anti-government protests in 2007 are thought to remain behind bars in Burma.

Ms Suu Kyi said all political prisoners must be freed - regardless of whether the government admitted their existence.

Burma, she said, had made progress but it was not "as fast as a lot of us would like it to be. But on the other hand I don't think it's too slow. It's slow but not too slow".

She called for Western countries to invest in Burma, which was suffering from "reputation risk".