But defender Charlie Daniels turned the ball into his own net for United's 93rd-minute equaliser.
Williams said: "It was disappointing but that is why Leeds is where they are in the league. They keep going until the final whistle and unfortunately for us we did not quite see out the job. We are still unbeaten this year but when you get that close to a win it is disappointing.
"I could not have asked for any more from the lads, and to be fair Leeds were much the stronger side in the first half and we did not look as if we had the belief. In the second half we did and we got ourselves in front."