The seven South Asian countries have agreed to grant the US and South Korea observer status in the South Asian Association for Regional Co-operation.
By Waliur Rahman
BBC News, Dhaka
At a meeting in the Bangladeshi capital, Dhaka, foreign ministry officials also finalised the details of Afghanistan joining the regional body.
China and Japan - the two Asian heavyweights - have already been granted observer status at Saarc.
The group's next summit is due to be held in 2007 in India's capital, Delhi.
"We have responded positively to the applications made by US and Korea seeking observer status of Saarc," Bangladeshi Foreign Secretary Hemayet Uddin told reporters after the meeting.
Guidelines outlining the observer role of China and Japan had also been finalised, Mr Uddin said.
The officials also finalised a draft of the declaration that would enable Afghanistan to become a full member of Saarc.
The country is due to sign the declaration at the Delhi summit.
Saarc's members are India, Pakistan, Bangladesh, Sri Lanka, Bhutan, Nepal and the Maldives.