GENEVA, April 23 (Reuters) - The United Nations Commission on Human Rights on Friday overwhelmingly adopted a resolution expressing concern about the scale of reported abuses in Sudan's Darfur region and agreed to appoint its own investigator.

But the United States -- the only member in the 53-state forum to vote against the resolution brought by African states -- slammed the text for failing to condemn "ethnic cleansing".

U.N. officials have accused Sudanese troops and Arab militias of raping, torturing and killing black Africans in the western area, equating such abuses with ethnic cleansing.

The commission, acting on the last day of its six-week annual session, overwhelmingly adopted the African text which had been endorsed by the European Union after negotiations.

The vote was 50 countries in favour, with one against (the United
States) and two abstentions (Australia and Ukraine), Australian chairman Mike Smith announced.

It later voted to shelve debate on a separate EU resolution which would have called on the government to ensure that attacks against civilians and "forced depopulations" are halted.

U.S. Ambassador Richard Williamson took the floor to denounce "horrific events" in the western region of Darfur, in which he repeatedly charged that 30,000 people had been killed in "racial and ethnic targeting".

"We fear a terrible famine to come when tens of thousands may well perish," the U.S. envoy added. "The Commission so far has failed to meet its responsibility today."

The U.N.'s food agency on Friday appealed urgently for hundreds of thousands of people it said were threatened by famine in Darfur, where rebels opened a new front against the government in February 2003. Some 900,000 people have been displaced internally and more than 110,000 have fled to Chad.

RIGHTS TEAM IN SUDAN

The diplomatic clash in Geneva coincided with U.N. human rights investigators holding talks in Khartoum with Sudanese officials before making a promised visit to the Darfur region.

The team, who interviewed refugees in Chad earlier this month, said in a report leaked on Wednesday that crimes against humanity were apparently being committed in a "reign of terror".

Williamson said on Friday that the United States would call for a rare special session of the Commission when the U.N. investigators reported back on their latest findings.

"Our work on ethnic cleansing in Sudan is not over. It is just beginning," he said.

Sudan's envoy took the floor after the vote to say: "We are convinced the situation in Darfur requires understanding on the part of the international community and also assistance to Sudan in its effort to find a peaceful and just solution."

"I affirm that my government will treat the Commission decision with great seriousness...," she added.

Egypt's envoy bluntly said: "We still believe that denunciations are not the way to deal with human rights. They are the easiest way, but certainly not the most effective."

For ideological reasons, African countries rarely support any motions critical of individual states at the annual talks, blocking any move over the past two years, for example, to censure the government of President Robert Mugabe in Zimbabwe.