Myanmar's military rulers threatened to ban Suu Kyi's National League for Democracy (NLD) last week, accusing it of links to "expatriate groups, terrorists and destructive groups" that they blame for attacks on the country.
Syed Hamid Albar, the Malaysian foreign minister, said closing down the NLD or not releasing Suu Kyi were "impediments and obstacles to creating visible signs of credibility in terms of the movement towards democracy".
"Even though we do not want to interfere in their affairs, they are not helping us in creating the necessary confidence in the international community," said Syed Hamid, who visited Myanmar in March as an envoy of the Association of South East Asian Nations (Asean).
"Even though we do not want to interfere in their affairs, they are not helping us in creating the necessary confidence in the international community"
Syed Hamid Albar,
Malaysian foreign minister
The NLD won elections in 1990 but was denied power by the military government, and Nobel Peace laureate Suu Kyi has spent about 10 of the past 15 years in various forms of detention.
Myanmar has proposed a seven-step "road map to democracy" and the government says step one, drafting a new constitution, is under way.
But its Asean neighbours say the process has been too slow.
The 10-nation group, known for its emphasis on consensus, has shown rare displeasure in recent years with Myanmar, which has been ruled by the military in different guises for more than 40 years.
At a meeting in Bali last month, Asean foreign ministers made their views known to Myanmar about its lack of progress towards democracy.
Syed Hamid reiterated that Asean would like to see Myanmar make visible changes, but would not put pressure on it.
The military has ruled the country
"They are not going to act on pressure. We are not going to pressure them ... We will keep on prompting them to listen to the views of Asean at least," he said.
Myanmar is seen as an obstacle to stronger trade ties with the European Union and the United States, both of which have imposed sanctions on the country, and Asean itself has come under pressure from the West to take stronger action against Myanmar, but it has ruled out expelling the country, saying there is no provision to do so.
Warning of 'terrorists'
Meanwhile on Thursday, the military government said that "terrorists" sent by anti-government groups and ethnic rebels were planning to bomb large cities in the country.
The state-run New Light of Myanmar newspaper reported that "bombers are planning to commit terrorist acts in harmony with above-ground politicians", a reference to the NLD.
Myanmar often blames rebels
such as the Karen for bombings
The newspaper said that government intelligence indicated that 19 terrorists planned to strike in Yangon, the commercial capital, and the second-largest city of Mandalay.
Security was tightened in Yangon, with police and soldiers stationed along main roads. Six explosions rattled the town centre last week, causing minor damage but no injuries.
The government often blames bombings on ethnic minority rebel groups.
One of the alleged terrorist groups was identified as the ethnic Karen National Union's 7th brigade, whose headquarters have come under attack as part of a huge offensive by the Myanmar army in Karen State in eastern Myanmar.
In recent months, the Myanmar army has launched a campaign that has driven at least 11,000 Karen villagers from their homes, aid groups say.