David Cameron is ready to signal the easing of sanctions against Burma when he makes a historic visit to the country tomorrow.
In what is believed to be the first ever visit to the former colony by a British Prime Minister, Mr Cameron will deliver a message of support to democracy activist Aung San Suu Kyi in person.
He is also due to meet President Thein Sein and congratulate him on pushing through democratic reforms.
Details of the trip emerged as Mr Cameron continued his trade mission to South East Asia.
At a joint press conference, Malaysian Prime Minister Najib Tun Razak urged his counterpart to relax sanctions.
Mr Najib, who recently held talks with Mr Thein in Burma, said: "I really do believe first of all that he is sincere.
"This has been supported by Aung San Suu Kyi's own personal remarks about him."
He went on: "We need to support a man like President Thein Sein so he will be supported by the community, because there will be elements who want to take a much more conservative approach."
Mr Cameron said developments in Burma may be "one potential chapter of light" in a "world where there are many dark chapters in history being written".
"Of course we should be sceptical. Of course we should be questioning. Of course we shouldn't be naive," he said.
But he added: "Aung San Suu Kyi herself, who has spent so many years in such a long, lonely but powerful struggle, believes that he is acting in good faith."
Britain had played a "leading role" in the imposition of sanctions, and would also not be "backwards" in responding to positive changes, he went on.
In a question-and-answer session with students at the Nottingham University campus in Malaysia later, Mr Cameron said: "I hope that, following my meetings tomorrow, I will have the confidence to go back to my country, back to others in the European Union, and argue that the change in Burma is irreversible, that they are set on a path towards democracy, that, in a world of difficulty and darkness and all sorts of problems, here is one bright light that we should encourage, and we should respond in a way that makes that regime feel that it is moving in the right direction and that the world is on its side."
Ten members of the business delegation who have been accompanying Mr Cameron around South East Asia are due to travel to Burma tomorrow.