Semantics

VOA

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.

What exactly is the difference between 'ethnic cleansing' and 'genocide'? And, if there is a difference, what is the purpose of a 'senior U.S. diplomat' pointing out the difference in this particular case? Will it determine the appropriate response from the U.S.?
One is entitled to demand, that the origins of the violence be properly addressed, as well as the responsibilities of the democratically elected (?) government of Kenya, those of the political opposition and of the international community. But what am I complaining about?! As we can see above, serious talks are taking place while, to quote a phrase, the people suffer.