Mousavi supporters rally support on Twitter

By Georgina Prodhan

LONDON (Reuters) - Supporters of defeated Iranian presidential candidate Mirhossein Mousavi posted defiant messages on Twitter on Tuesday, calling for a second banned pro-Mousavi rally to go ahead and offering security updates.

Social networking websites such as Twitter and Facebook have become a focal point for young, urban Iranians opposed to President Mahmoud Ahmadinejad, who defeated Mousavi in Friday's presidential election and whose government controls the state media.

"Alert: Mousavi march still on. 5PM," read one short message, or "tweet," on Twitter.

"Good luck at the march. Don't take cars, they will be waiting for you when you return to them," read another, as tweets on the subject of the Iranian election poured onto the site every few seconds.

A U.S. official said meanwhile that the U.S. State Department had contacted Twitter at the weekend to urge it to delay a planned upgrade that could have cut daytime service to Iranians.

"We highlighted to them that this was an important form of communication," the official said of the conversation the department had with Twitter. The official, speaking in Washington, declined further details. The request was made despite the Obama administration's stated concern not to meddle in the post-election dispute.

Twitter had said earlier it had delayed the upgrade, without mentioning any contact with the U.S. government.

BLOCKED TEXT MESSAGES

The Iranian government blocked SMS text messages during polling after opposition candidates used them to galvanize key young voters during the fiercely contested election campaign, and Tehran residents were still unable to send SMSs on Monday.

The BBC's Persian service was also blocked.

Social networking site Facebook, which has about 150,000 members in Iran, said on Monday it had had reports that some users in Iran were having difficulties accessing Facebook.

"This is disappointing, especially at a time when citizens are turning to the Internet as a source of information about the recent election," it said in a statement.

Twitter Inc said in a blog post on its site it was delaying a planned upgrade because of its role as an "important communication tool in Iran." The hourlong maintenance was put back to 5 p.m. EDT/2100 GMT, which corresponds to 1:30 a.m. on Wednesday in Iran.

It said the upgrade had originally been planned for Monday night in the United States, which would have cut daytime service in Iran on Tuesday.

Unrest has rocked Tehran and other cities since the Interior Ministry released results on Saturday that showed hard-liner Ahmadinejad had defeated Mousavi by a landslide.