The Association of Southeast Asian Nations (ASEAN) has tasked a senior Brunei official with visiting Myanmar to meet all parties to seek an end to the turmoil that has wracked the country since the military seized power in February.

But the nation's military authorities have indicated they will not permit a meeting with Suu Kyi, prompting some ASEAN members to threaten to exclude junta chief Min Aung Hlaing from a summit later this month.

The Myanmar foreign ministry said the country had shown "flexibility in any possible ways and means" to accommodate special envoy Erywan Yusof's visit.

But it said some of his requests "go beyond the permission of existing laws" and urged him to prioritise meeting government officials and members of "legally existing political parties".

The rebuff follows a warning from the junta earlier this month that it would be "difficult" for the envoy, who is Brunei's second foreign minister, to meet people facing trial.

Nobel peace laureate Suu Kyi, 76, is currently on trial on a host of charges ranging from sedition to flouting coronavirus restrictions.

ASEAN foreign ministers will hold a virtual meeting on Friday where they may decide on whether to send the envoy under the junta's conditions and whether to invite Myanmar to the summit.

The bloc appointed Yusof in August after lengthy wrangling as pressure mounted for action on Myanmar, where nearly 1,200 civilians have been killed during protests and a military crackdown since the coup.

The State Administration Council, as the military government calls itself, has promised to hold elections and lift a state of emergency by August 2023.

It has justified seizing power by pointing to allegations of vote rigging in last year's election, which Suu Kyi's party won comfortably.