US President Barack Obama 'tweeted' his very first message on Monday, joining the millions who have used the Twitter micro-blogging site as a vital information vehicle for the Haiti disaster.

The president and First Lady Michelle Obama visited an unadorned office in the American Red Cross headquarters serving as a disaster operations center, and lent encouragement to staff and volunteers helping coordinate humanitarian aid activity in earthquake-devastated Haiti.

"We're just here to say 'thank you' for the great work you're doing," Obama said as he entered the operations center with American Red Cross board chairwoman Bonnie McElveen-Hunter.

As he moved about the room, where large maps of Port-au-Prince were tacked to the walls, he stopped at a media team desk and hit the "Send" button on a message that had just been typed on Twitter: "President Obama and the First Lady are here visiting our disaster operation center right now."

This was followed by: "President Obama pushed the button on the last tweet. It was his first ever tweet!"

During his presidential bid in 2007 and 2008, Obama's team harnessed the power of the Internet to raise record funding for his campaign.

His administration, too, has been praised for its tech-savvy use of the web.

It has included live streams of the president's speeches onto social networking sites like Facebook, and the White House has its own Twitter account.

But apparently Obama himself had yet to personally embrace the phenomenon until now.

The Internet, especially Twitter and social networking sites, have been instrumental in helping people locate relatives in Haiti or plead for help to find loved ones, post pictures or links to video from the earthquake zone.

The web has also been a spectacular emergency fund-raising tool.

More than 22 million dollars for Haiti's earthquake survivors has been collected by text-messaging a Red Cross appeal in the United States, the State Department said Monday in its own Twitter message.