Tevez thought he should have had a spot-kick in normal time at Wembley when Hreidarsson grabbed his legs in the penalty area, although the Portsmouth left-back insists he was reacting to the United player trampling on him.
The incident ended with Tevez grabbing Hreidarsson's throat, although referee Peter Walton waved play on and took no action against either player.
Hreidarsson, after United had won 3-1 on penalties, said: "I was down and he stamped on me. I thought he could have avoided me, there was no need for it.
"That was why I reacted and why I grabbed his leg."