The Football Association will speak to both Manchester clubs to remind them of their responsibilities before next week's Carling Cup semi-final decider at Old Trafford. It is expected the FA will officially confirm Gary Neville will face no sanction over his one-fingered gesture to Carlos Tevez during Tuesday's first-leg, when City won 2-1.
Nevertheless, the FA acknowledge the simmering tension between the two sides could lead to an escalation of the problem next week, when the teams face each other once more to decide who will face Aston Villa at Wembley on February 28.
The FA hope the two clubs heed their informal message given the huge number of people who will be watching a match which has captured attention far beyond the city itself.