The US treasury department has eased sanctions on Iran, Cuba and Sudan to help further the use of web services and support opposition groups.
US technology firms will now be allowed to export online services such as instant messaging and social networks.
Companies had not offered such services for fear of violating sanctions.
Opposition supporters in Iran used social networking sites and services to organise protests after the country’s disputed presidential poll last year.
The US Treasury said exports would be allowed of services related to web browsing, blogging, email, instant messaging, chat, social networking and photo- and movie-sharing.
