Leeds council chiefs face a nervous wait to see if the Government will approve their arena funding plans.
Fears are growing over a last-ditch attempt by Sheffield to force the scheme off course.
A decision on regional development agency Yorkshire Forward's proposed 18m support for the project had been expected yesterday – but the council was instead told an announcement would not be made until next week.
The decision sparked fears Sheffield will exploit the delay. Its MPs say publicly-funded Yorkshire Forward should not invest in a scheme that favours one part of the county over another.
A report on Wednesday claimed Sheffield arena would lose more than 1.8m a year if the West Yorkshire project got the go-ahead.
Sheffield arena managers commissioned the study even though Yorkshire Forward's decision to back the Leeds scheme was made after what it has described as an "extensive, independent evaluation".
Coun Andrew Carter, the council's executive board member with responsibility for the Leeds arena, said: "Sheffield's report is rather like a tobacco company carrying out a study into the health effects of smoking.
"South Yorkshire's politicians cannot be allowed to succeed with their outrageous attempts to disrupt our plans."
If the Government approves Yorkshire Forward's investment, the remaining 60m needed for the arena would be supplied by the council itself.
About two-thirds of that cash would be borrowed, with the rest coming from the proceeds of the sale of Leeds Bradford Airport.
The local authority wants construction work to start by the end of next year on the Clay Pit Lane site it has earmarked for the 12,500-seater concert venue.