Mark Baker, Manila – Burma's military regime has sparked a rift within the Association of South-East Asian Nations by blocking moves towards East Timor joining the regional grouping after the country achieves independence next year.

The Burmese have vetoed a decision to grant East Timor observer status within Asean – a first step to full membership – in protest at links between senior Timorese leaders and the detained Burmese democracy leader, Aung San Suu Kyi.

The veto, exercised at an informal meeting of Asean foreign ministers in Thailand last week, has angered several member states who believe East Timor's eventual membership is important to advance regional security and economic co-operation.

The Philippines Government has now stepped up pressure for ASEAN to amend its long-standing convention of consensus decision-making to prevent a single member blocking agreement between the rest of its 10 members.

Brunei, which will host this year's annual ASEAN meetings in July, has indicated its dissent by inviting East Timor to attend – not as a formal observer but as a "special guest of the chair".

Philippine officials and East Timor's Foreign Minister, Jose Ramos Horta, said Burma was the only dissenter when East Timor's application for observer status was debated by the foreign ministers. Mr Ramos Horta said he was disappointed by the decision, which had been expected because of links between the Burmese democracy movement and the Timorese resistance during its struggle for independence from Indonesia.

Mr Ramos Horta has spoken out strongly in support of Aung San Suu Kyi, whose National League for Democracy won a landslide election victory a decade ago but was blocked from power by the military. Ms Suu Kyi has remained under virtual house arrest for the past 18 months despite intermittent peace talks with the regime.

"It is in the interests of ASEAN that they embrace East Timor rather than trying to keep it out," Mr Ramos Horta said. "It is important for peace and regional stability."

There was considerable support among existing ASEAN members for the Burmese democracy movement, including from Indonesia, whose President Megawati Sukarnoputri has publicly expressed solidarity with Ms Suu Kyi, he said.

"The Burmese should not worry that we would be unhelpful and uncooperative within ASEAN. An independent East Timor would work with its neighbours on regional matters rather than taking unilateral positions."

Mr Ramos Horta, who, like Ms Suu Kyi, is a Nobel peace laureate, said he had been instrumental in persuading 20 other Nobel laureates to modify a statement on Burma published in December to give "constructive and balanced acknowledgement of steps towards progress" in the country's political standoff.

Mr Ramos Horta said he accepted the view of several ASEAN members, including Singapore, that East Timor would not be ready to meet the requirements of full membership for a number of years. East Timor has also applied for observer status with the South Pacific Forum.