"George Bush doesn't care about black people," West said from New York during the show aired live on Friday on the East Coast on NBC, MSNBC, CNBC and Pax, just before cameras cut away to comedian Chris Tucker.
West, who is black, suggested moments earlier that delays in providing relief to survivors of the hurricane that hit the US Gulf Coast on Monday and flooded New Orleans were deliberate.
He said America was set up "to help the poor, the black people, the less well-off as slow as possible".
"We already realised a lot of the people that could help are at war right now, fighting another way, and they've given them permission to go down and shoot us," the Grammy award-winning singer, who was paired with comedian Mike Myers, also said in what NBC described as unscripted remarks.
The rapper was apparently referring to shoot-on-sight orders issued to National Guard troops to halt violence and looting in New Orleans.
West also criticised the media's portrayal of blacks, saying: "I hate the way they portray us in the media. If you see a black family, it says they're looting. See a white family, it says they're looking for food."
In a statement, NBC said: "Kanye West departed from the scripted comments that were prepared for him, and his opinions in no way represent the views of the networks.
The hurricane left widespread
devastation and caused havoc
"It would be most unfortunate if the efforts of the artists who participated tonight and the generosity of millions of Americans who are helping those in need are overshadowed by one person's opinion."
The programme, hosted by Matt Lauer of NBC News, urged viewers to donate to the American Red Cross Disaster Relief Fund.
It included 18 presenters, and featured performances by New Orleans natives Harry Connick Jr and Wynton Marsalis, as well as Louisiana native Tim McGraw and Faith Hill of Mississippi, which was also struck by Katrina.