Secretary of State Hillary Clinton said Monday a US decision to allow exports of Web tools to Iran was intended to allow Iranians to "communicate without being blocked by their own government."

The Treasury Department on Monday eased sanctions on Iran, Cuba and Sudan to allow exports by US companies of services related to Web browsing, blogging, email, instant messaging, chat, social networking and photo- and movie-sharing.

"We're supporting the right of free expression," Clinton told reporters.

She said the move would "provide Internet tools to citizens of Iran so that they can communicate, so that they can have other sources of information about what is going on inside their country.

"We believe that (if) Iran calls itself a democracy it should act like one and that means respecting the right to free expression and assembly of its own people," Clinton said.

"And in the 21st century, expression and assembly are carried out on the Internet as well as in person," she said. "So we're going to continue to support those Iranians who wish to circumvent and be able to communicate without being blocked by their own government."

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

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.

"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.

A Google spokesman welcomed the Treasury move.

"We're very happy with the decision of the US Treasury Department to allow the export of Internet communications software and services to Iran and other sanctioned nations where freedom of expression is limited," the spokesman told AFP.

"We have long advocated for the ability to provide citizens of those countries tools to help them communicate with each other and the world," he said. "We'll be exploring how we might provide our communications products to them."

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.

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.