Vieira denied threatening Gary Neville before Keane stepped into the stand-off as the teams walked down the tunnel before Arsenal's 4-2 defeat.

Referee Graham Poll, who had to separate the pair, confirmed in his official report he dealt with the matter to his satisfaction.

"He has confirmed that he is satisfied that he dealt with the incident at the time. Therefore no further action is required," the FA said in a statement.

The last time the teams played, at Old Trafford in October, an Arsenal player was accused of throwing a pizza and soup at United boss Alex Ferguson.

United seized command in the second-half on Tuesday and having twice come back from behind, Cristiano Ronaldo put them ahead before John O'Shea lobbed a late fourth in what was eventually a comfortable victory.

Chelsea can now extend their advantage over Arsenal to 13 points by winning at Blackburn on Wednesday, even if Vieira refused to give up just yet.

"It will be difficult, of course. Chelsea need to lose points and we have lost at home to one of our main rivals," insisted the midfielder.

"But we just have to go on and try to win our next game, and not think about Chelsea or United. We just have to improve on how we played." as we can."