Malaysia's foreign minister expressed disappointment Monday at Myanmar's failure to cooperate with an ASEAN envoy, warning that the country's junta chief could be excluded from an upcoming summit of the bloc.

The Association of Southeast Asian Nations (ASEAN) has been under pressure to address a February coup in Myanmar and subsequent crackdown on dissent that has killed more than 1,100 people.

Members of the 10-nation group have pushed for an end to the troubles, with a Bruneian official chosen as an envoy due to visit Myanmar to meet with the opposing factions.

But an apparent reluctance to grant the envoy access to ousted leader Aung San Suu Kyi rankled Malaysia during a video call between ASEAN foreign ministers on Monday.

"We are disappointed that the Myanmar authorities have not cooperated with the Special Envoy of the ASEAN on Myanmar," Malaysian foreign minister Saifuddin Abdullah said on Twitter.

"Unless there is progress, it would be difficult to have the Chairman of the SAC at the ASEAN Summit," he added, referring to Myanmar's junta chief Min Aung Hlaing.

Leaders of the Southeast Asian bloc are due to hold a summit at the end of October.

Singapore foreign minister Vivian Balakrishnan said on Twitter that officials had urged Myanmar to work with the envoy during the call.

Brunei second foreign minister Erywan Yusof was chosen as the envoy in August after months of negotiations, but Myanmar has yet to give details of his planned visit.

On Thursday, a junta spokesman said it would be "difficult" for the envoy to hold talks with people on trial and the regime was more open to meetings with "official organisations".

Suu Kyi, 76, faces charges including flouting coronavirus restrictions during polls last year that her party won in a landslide, illegally importing walkie-talkies and sedition.

She faces decades in prison if convicted on all charges.

The junta has promised to hold elections and lift a state of emergency by August 2023.