Myanmar has been racked by a deadly crackdown on protests, economic collapse and a refugee exodus since the coup. A surge in coronavirus infections has overwhelmed its health system, worsening the humanitarian crisis in the past month.
The search for a special envoy began in April, when ASEAN leaders produced a "five-point consensus" to tackle the turmoil in Myanmar. U.N. and U.S. officials have in recent weeks urged ASEAN to expedite the appointment of the special envoy.
The second minister for foreign affairs of Brunei, Erywan Yusof, said on Friday night he hoped a final decision would be made on Monday. Brunei is chair of ASEAN this year.
"Without the envoy leading the way, it is very difficult" to address the situation in Myanmar, he said.
ASEAN - whose members include democracies, one-party communist states and authoritarian governments - has been deeply divided on the envoy, and has discussed appointing more than one to break the deadlock.
Four regional diplomatic sources said Erywan was favoured to become envoy and be assisted by "advisers". But a meeting of senior ASEAN officials on Thursday failed to reach agreement, they said.
As well as the nine other ASEAN members, Myanmar's military regime will have to approve the appointment, they said.
The country's military ruler, Min Aung Hlaing, said in a speech on Sunday that Myanmar had favoured Thailand's former deputy foreign minister Virasakdi Futrakul as envoy, but "new proposals were released and we could not keep moving onwards".
"Myanmar is ready to work on ASEAN cooperation within the ASEAN framework, including dialogue with the ASEAN special envoy in Myanmar," he said.
A spokesman for Sasa, Myanmar's National Unity Government that opposes the military junta, said the envoy must "put the people of Myanmar front and centre".
"Anything that can help alleviate the people's suffering is welcome," he said.
Erywan publicly confirmed he was one of four candidates. Diplomats said the others were Thailand's Futrakul, former Indonesian foreign minister Hassan Wirajuda and veteran Malaysian diplomat Razali Ismail.
ASEAN will also announce a proposal for aid to Myanmar, including support to combat the pandemic, diplomats said.
(Reporting by Tom Allard in Jakarta, Panu Wonngcha-un in Bangkok and Ain Bandial in Bandar Seri Begawan; editing by Christopher Cushing and Mark Heinrich) ((Tom.Allard@thomsonreuters.com; +628118718540;))