UPDATE 2-Colin Powell and Bill Gates join malaria campaign

* Campaign aims to buy bednets to fight malaria

* Participants include Ryan Seacrest and Shaquille O'Neal (Adds comment from U.S. mayor, amends bednets figure para 8)

By Alex Dobuzinskis

LOS ANGELES, April 21 (Reuters) - Former U.S. Secretary of State Colin Powell, billionaire Bill Gates and Queen Rania of Jordan will put their fame to work this week as they join a Twitter campaign to end malaria deaths.

Ashton Kutcher, Ryan Seacrest and other Hollywood celebrities have also joined the Twitter campaign. Starting on Wednesday, the participants will send out "tweets" encouraging the public to donate to buy bednets which guard against the mosquitoes that spread malaria in Africa.

Gates will also take part in TV charity fundraiser "Idol Gives Back" on Wednesday to promote the fight against malaria and other health causes.

Organizers of the Twitter fund-raising push are working with the United Nations Special Envoy for Malaria, Ray Chambers.

"It's one of the few campaigns I'm aware of where $10 buys a bednet which can save a child's life," Chambers told Reuters. "The tangible feel of it is greater than any other campaign I've been exposed to."

Malaria causes more than 1 million deaths annually worldwide, but the problem is most acute in Africa.

The UN aims to reduce the deaths from malaria to near zero in Africa by 2015. So far, more than $4 billion has been raised to fight the disease, mostly from the World Bank, government agencies and the Bill and Melinda Gates Foundation.

The UN expects to cover 700 million people at risk of malaria with bednets, but it is still short of funding for roughly 50 million of those nets, Chambers said.

NO IDLE CAMPAIGN

On Wednesday, singing contest "American Idol," the top-rated program on U.S. television, holds its "Idol Gives Back" show. That too will ask for public donations for malaria relief, as well as charities working with children and poverty in the United States.

"Idol Gives Back" is supported by News Corp (NWSA.O), Ford Motor Co (F.N), Exxon Mobil Corp (XOM.N), AT&T Inc (T.N) and Coca-Cola Co (KO.N).

Others taking part in the Twitter campaign include basketball star Shaquille O'Neal, talk show host Larry King, singer Jordin Sparks and Sarah Brown, the wife of British Prime Minister Gordon Brown, organizers said.

"Awareness is the pre-requisite of action -- if people don't know about an injustice they won't fight to end it," Brown said in an e-mail to Reuters.

The Twitter campaign is a way to build that awareness, because collectively, the participants have 50 million followers on social networking site Twitter.

Cory Booker, the mayor of Newark, New Jersey, and one of the figures in the campaign, said Twitter is important because users actively seek out information from those they follow.

"These are folks that really want to know what's on a person's mind," he told Reuters.

This year, the Case Foundation will match up to $25,000 of the donations made through the campaign.

"It's matched by real funding that's going to buy real nets for real people," said Biz Stone, co-founder of Twitter, who will also be one of the figures sending out tweets.

This first blast of messages over Twitter will end on Sunday, which is World Malaria Day. It will be followed later in the year by more tweets from the participants. (Reporting by Alex Dobuzinskis: Editing by Jill Serjeant)