According to him, any attempts to add an extra tier to the Sir Bobby Charlton stand would be a massive engineering challenge.
The work required to expand the stadium from the current capacity of 76,000 will have to take place over a number of seasons if plans are approved.
“We haven’t left the easiest stand until last. The Sir Bobby Charlton Stand is the last unexpanded stand.
“There’s not much space on either side of the stand meaning that it’s a very complex engineering challenge.
“It would be a multi-season challenge and it isn’t certain there’s a way of doing it which doesn’t render us homeless,” Arnold told South China Morning Post.