Kanaan claimed his first win of the season

Points leader Wheldon looked on course for his fifth win in eight races when he overtook defending race champion Buddy Rice with three laps remaining.

But Kanaan passed him on the next lap and held on to win by 0.012 seconds.

Vitor Meira was third, with another Andretti driver, Dario Franchitti, in fourth place.

Defeat was harsh on Wheldon, who had struggled to find form all week but led for 111 laps, having started from 11th place.

"I love Tony to bits," he said.

"I'm glad he beat me instead of somebody else, but losing like this is difficult to take."

Danica Patrick, only the second woman in Indy Racing history to start from pole, finished ninth.

Race result from Argent Mortgage Indy 300, Kansas City:
1 Tony Kanaan (Brz) Andretti Green Racing 200 laps
2 Dan Wheldon (GB) Andretti Green Racing 200 laps
3 Vitor Meira (Brz) Rahal Racing 200 laps
4 Dario Franchitti (GB) Andretti Green Racing 200 laps
5 Tomas Scheckter (SA) Panther Racing 200 laps
6 Scott Sharp (US) Fernandez Racing 200 laps
7 Darren Manning (GB) Chip Ganassi Racing 200 laps
8 Helio Castroneves (Brz) Penske 200 laps
9 Danica Patrick (US) Rahal Racing 200 laps
10 Buddy Rice (US) Rahal Racing 200 laps