* Doctor asked Farrow to end hunger strike
* Richard Branson to fast for three days
(adds comment from Branson, paragraphs 4-5)
UNITED NATIONS, May 8 (Reuters) - Actress Mia Farrow, ailing after almost two weeks on a hunger strike, announced on Friday that British billionaire Richard Branson would take over her protest in solidarity with people in Sudan's Darfur region.
A Farrow spokesman said her health had deteriorated in the past few days and her doctor requested that she end the liquids-only fast she began 12 days ago to protest at Khartoum's expulsion of more than a dozen aid agencies from Darfur.
Farrow asked Branson to take over the fast, her statement said, adding that the British entrepreneur had accepted and would begin a three-day hunger strike on Friday.
"I'm honoured to be taking over the fast for the next three days," the founder of the Virgin Group said in a statement on his blog.
"We cannot stand and watch as 1 million people suffer. We all need to stand up and demand that international aid is restored and that the people of Darfur are protected and given the chance to live in peace."
Farrow's spokesman said last month that her doctor expected the slightly built actress could not fast for more than three weeks.
Farrow, who was appointed Goodwill Ambassador for the U.N. children's agency UNICEF in 2000, has been campaigning for years to raise funds for children in conflict zones such as Darfur, Democratic Republic of the Congo, Haiti, Chad and Nigeria.
The International Criminal Court issued a warrant for the arrest of Sudanese President Omar Hassan al-Bashir in March, charging him with masterminding mass killings and deportations in Darfur in western Sudan.
Since then, Sudan has expelled 13 foreign and three domestic humanitarian aid agencies, accusing them of collaborating with the Hague-based ICC.
U.N. Secretary-General Ban Ki-moon said in his latest report on the joint U.N.-African Union peacekeeping mission in Darfur, known as UNAMID, that the expulsions had put "over 1 million people at life-threatening risk" in Darfur.
U.N. officials say that as many as 300,000 people have been killed and more than 2.7 million driven from their homes in Darfur in almost six years of ethnic and political violence.
Khartoum, however, says 10,000 people have died. Some 4.7 million people rely on humanitarian aid in Darfur. (Editing by Bill Trott)
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