Two leading American business groups say firms operating in ASEAN countries are sceptical the bloc can meet a 2015 deadline to establish a single market.
The 10-member Association of Southeast Asian Nations (ASEAN) has set 2015 as the target for creating a single regional economic market known as the ASEAN Economic Community (AEC).
In a survey of 475 senior US business executives from the region - published on Tuesday and conducted by the American Chamber of Commerce in Singapore and the US Chamber of Commerce - 52 per cent said they "do not think that the AEC's goals will be realised by 2015".
Of those who doubt ASEAN will reach its deadline, nearly 60 per cent "think that ASEAN will not reach AEC's goals until 2020 or later".
Only 23 per cent of all executives questioned believe that ASEAN will meet its 2015 goal, the poll showed.
Despite their scepticism, the survey showed that US companies are optimistic about overall business prospects in the region.
US firms said their level of trade and investment in ASEAN rose over the past two years and expect this figure to climb over the next five years.
Indonesia was named the most attractive country for new business expansion, followed by Vietnam, Thailand and Myanmar.
Meanwhile the Philippines showed the biggest improvement in its business environment between 2008 and 2013, the survey said.
ASEAN, a region of 600 million people, wants to establish a common market and manufacturing base so that it can better compete as a group with giant neighbours such as China and India in terms of trade and investments.
While it has made strides in bringing down tariff barriers to trade in goods, services and investments, analysts have said the problem of creating a single market lies in removing non-tariff hurdles.
The group comprises Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam.