The Reds center back gave the ball straight to Victor Anichebe, who buried the equalizer as West Brom battled back for a 1-1 draw Sunday.
With the Reds leading 1-0 thanks to a Daniel Sturridge goal, the Ivorian presented the ball straight to the feet of Victor Anichebe on the edge of the box, with the former Everton man punishing the mistake by firing home and earning his side a point.
Toure was frustrated with his mistake as Liverpool missed out on what would have been a fourth win in five matches.
"It was a terrible pass by me," the center back told The Liverpool Echo. "I should have passed to one of our players but instead I passed it straight to the striker.
"I just didn't see [Anichebe]. I should have played it to Aly [Cissokho] on the side. I made a very bad pass. I don't know why I passed the ball into the middle of the pitch, it was crazy.
"I'm disappointed for me and the team. It's hard to take, especially for me, because we played well. The manager knows how disappointed I am. My pass put the team in a difficult situation."