A senior U.S. diplomat says "ethnic cleansing" is underway in Kenya's Rift Valley in the aftermath of last month's disputed presidential election, but she says the violence does not rise to the level of genocide.

Assistant Secretary of State for African Affairs Jendayi Frazer told reporters Wednesday in Addis Ababa, Ethiopia that the aim of the violence in the Rift Valley is to push certain people out of the region.

Frazer said the United States is reviewing its aid to Kenya in light of the political turmoil there.

More than 800 people have died in the post-election violence in Kenya.

Kenya's feuding political rivals - President Mwai Kibaki and opposition leader Raila Odinga - have started talks aimed at resolving the crisis under the mediation of former U.N. chief Kofi Annan.

Mr. Odinga has accused Mr. Kibaki of rigging his re-election.

Mr. Annan said he is confident the immediate political issues could be resolved within four weeks and that broader issues could be solved within a year.

Mr. Odinga said the sides urgently need to address what he called the flawed results of the election. Mr. Kibaki did not mention the vote but said he is glad to address underlying issues that caused the violence.

U.S. Secretary of State Condoleezza Rice and European leaders on Tuesday urged Kenya's leaders to work with Mr. Annan to broker an end to the violence.

Tuesday's talks in Nairobi began just hours after gunmen killed a Kenyan opposition lawmaker, Mugabe Were, at his home in the capital, triggering ethnic clashes that killed at least four people.

Ethnic violence across central and western Kenya has killed scores of people in the last week. Much of the violence has involved clashes between Mr. Odinga's Luo tribe and the Kikuyu tribe of Mr. Kibaki.