I think he definitely knew what his intentions where... that is, to kill Obi-Wan. And if he could kill him he would have, but he never got the chance. Obi-Wan fought well.
It's the whole 'high ground' thing, which I think is kinda cheap. Obi-Wan had the high ground, which gave him the advantage over Anakin. For Anakin to get the advantage he needed to jump to higher ground. I guess the logic being that whoever was on the high ground would push the other into the lava either by force or duelling...