The US Treasury Department on Monday eased sanctions on Cuba, Iran and Sudan to give citizens of those countries access to email, instant messaging, social networks and other Internet-based services.

"Today's action will enable Iranian, Sudanese and Cuban citizens to exercise their most basic rights," Deputy Treasury Secretary Neal Wolin said.

Lifting the ban on exports of software and services "will make it easier for individuals in Iran, Sudan and Cuba to use the Internet to communicate with each other and with the outside world," Wolin said in a statement.

The Treasury Department said the move would allow exports by US technology companies of services related to Internet browsing, blogging, email, instant messaging, chat, social networking and photo- and movie-sharing.

Requested by the State Department, the Treasury Department said the easing of sanctions was intended to "ensure that individuals in these countries can exercise their universal right to free speech and information to the greatest extent possible."

"As recent events in Iran have shown, personal Internet-based communications like email, instant messaging and social networking are powerful tools," Wolin said. "This software will foster and support the free flow of information -- a basic human right -- for all Iranians.

"At the same time as we take these steps, the administration will continue aggressively to enforce existing sanctions and to work with our international partners to increase the pressure on the government of Iran to meet its international obligations," Wolin added.

Cuba, Iran and Sudan all exert varying degrees of control over the Internet and it was not apparent what immediate impact the Treasury Department's move would have.

Certain services from Web giants such as Google's email program Gmail are already used in countries on US sanctions lists such as Iran.

But Google and other companies have blocked access to other services for fear of violating US laws which ban commerce with black-listed countries such as Cuba, Iran and Sudan.

Opposition supporters in Iran used social networking sites and services such as Twitter, Facebook and Google-owned YouTube in their communications efforts following the country's disputed presidential election last year.

During protests in Iran in June, the State Department took the unusual step of asking Twitter to delay planned maintenance because of its use by Iranian opposition supporters.

In a speech on Internet freedom in January, US Secretary of State Hillary Clinton condemned "electronic barriers" and said Washington stands for "a single Internet where all of humanity has equal access to knowledge and ideas."

"Countries that restrict free access to information or violate the basic rights of Internet users risk walling themselves off from the progress of the next century," she said.

The United States has imposed an economic embargo on Cuba since 1962 and banned virtually all trade with Iran and Sudan since 1997.

US lawmakers on Monday called for even tougher sanctions on Iran because of the Islamic Republic's nuclear program.

Sudan has been on the sanctions list as an alleged supporter of Islamic militant groups and over the situation in war-torn Darfur.

In the spirit of social networking, the Treasury Department used its newly created Twitter account to send a "tweet" about the easing of sanctions.