David Cameron and Myanmar's opposition leader have called for the suspension of economic sanctions against the South Asian nation after holding landmark talks.
The British prime minister met Aung San Suu Kyi on Thursday at her lakeside home where she was held under house arrest for 22 years by the country's military government.
"If we really want to see the chance of greater freedom and democracy in Burma, we should respond when they take action," Cameron said.
"For the sake of a country that has been crying out for freedom after decades of dictatorship, and that is crying out for a stronger economy after so much grinding poverty, it must be worth taking that risk."
Cameron said an arms embargo against Myanmar should remain but it was right to suspend, but not lift, remaining sanctions.
The visit was the first by a British prime minister in decades and comes amid thawing relations between the once-pariah state and Western nations.
Earlier, Cameron met Thein Sein, Myanmar's reformist president, who took over from Than Shwe, the general who was was in charge as Suu Kyi and other political prisoners' rights were violated.
The European Union is due this month to review its sanctions in response to political and economic reforms undertaken by the civilian government that came to office a year ago when the military government partially ceded power.
Quoting a source from Cameron's office, the Reuters news agency said it was unlikely all EU sanctions against Myanmar would be lifted.
"We will want that decision on the 23rd of April to be the right balance that recognises the great progress that's been made ... versus not taking our foot too much off the pedal and going backwards," the source added.
Britain, Myanmar's former colonial ruler, has traditionally stuck to sanctions because of human rights concerns and its shift is likely to clear the way for a suspension of the measures later this month.
'Thein Sein genuine'
Suu Kyi, a Nobel Peace Prize laureate whose support is seen as crucial for any easing of the sanctions, including those imposed by the US, also called for a suspension of the measures.
"This would strengthen the hands of the reformers - not just the suspension but the fact that there is always a possibility of sanctions coming back again if the reforms are not allowed to proceed smoothly," she said.
"We still have a long way to go but we believe that we can get there. I believe that Thein Sein is genuine about democratic reforms."
Cameron said people should be "under no illusion about what a long way there is to go", and said Myanmar's leaders want to demonstrate that moves towards democracy were "irreversible".
The fact that Myanmar has been "largely unexploited in terms of business opportunities" is part of what is driving a steady stream of foreign dignitaries, including Hillary Clinton, the US secretary of state, and her British counterpart, William Hague, to the nation, Al Jazeera's Wayne Hay, reporting from neighbouring Thailand, said.
Myanmar's military rulers ceded power to a quasi-civilian government following a November 2010 election marred by opposition complaints of rigging, and won by a party set up by the military.
"In a world where there are many dark and depressing chapters of history being written there is a potential chapter
of light," Cameron said ahead of his visit.
"Of course we should be sceptical, of course we should be questioning."
The new government has released hundreds of political prisoners and introduced a wave off reforms including loosening media controls, allowing trade unions and protests, talks with ethnic minority rebels and sweeping economic changes.
In parliamentary by-elections earlier this month, Suu Kyi was elected to Myanmar's parliament after decades as a prisoner.
The last election she won under her NLD party in 1990 was not recognised by the military government.