Tough new US sanctions on military-ruled Myanmar have forced textile factory closures and put tens of thousands out of work since the trade ban was announced a month ago.

The sanctions, which officially took effect on Thursday, close the US market to imports from Myanmar, where pro-democracy leader Aung San Suu Kyi has been detained by the junta for nearly three months.

Yangon businessmen said 100 of Myanmar''s 300 textile and garment factories had closed in anticipation of the move - leaving tens of thousands of workers, mostly young women, jobless.

The United States bought US$356 million (S$630 million) worth of textiles, clothing, footwear and other goods from Myanmar last year - about 10 per cent of its exports.

''We hear that 100 garment factories have closed because the US market refused their products,'' said Mr Win Sein, managing director of a leading import-export company.

''This is the beginning and the worst is to come. The US says the sanctions are meant to squeeze the government. In fact, it is the public who are the first and worst hit.''

The US accounts for some 80 per cent of exports from the industry, set up with South Korean, Taiwanese and Hong Kong investment. The industry employs 350,000 people.

Yangon is facing international pressure to free Nobel laureate Suu Kyi, detained since a May 30 clash between her supporters and a pro-government group.

The European Union has targeted more Myanmar officials for visa bans and asset freezes. It has also suspended trade privileges over Myanmar''s alleged use of forced labour.

Japan, a key donor, has suspended fresh aid to the country.Yangon has remained defiant and state-run media carried fresh denunciations of Washington on Thursday.

''The US government''s tough economic sanctions on developing countries, including Myanmar, will fuel hatred and international conflict, and harm international friendship, stability and cooperation,'' said the New Light of Myanmar newspaper.

Myanmar''s South-east Asian neighbours have delivered an unprecedented rebuke over Ms Suu Kyi''s latest detention, but they do not favour economic sanctions.