Rangers want season extension as fixture pile-up looms
And, even if Walter Smith's men lose out to Fiorentina in the semi-final, the Ibrox club will object if they are asked to play four league games over an eight-day period.
Sunday's Scottish Cup replay victory over Partick Thistle clinched a weekend Hampden date with St Johnstone and keeps alive the club's hopes of a domestic Treble.
But it is the chase for UEFA Cup glory that has put Rangers on an SPL collision course.
For Sportsmail can reveal they will forcibly fight their corner with the SPL if they succeed in knocking out the Italians to clinch a place in the UEFA Final at the City of Manchester Stadium on Wednesday, May 14.
It is understood that chief executive Martin Bain would be prepared to appeal for help and ask for the Saturday, May 10 Ibrox fixture against United to be rearranged, even though United will put tickets on sale.
Rangers are aware of the 2003 precedent when Celtic were given eight clear days to prepare for their UEFA Cup Final appearance against Porto in Seville after a scheduled weekend match against Dundee at Parkhead was brought forward by the SPL to the previous midweek.
The Ibrox club also noted with interest that the SPL issued a media release last Friday trumpeting Scottish football's rising coefficient in the wake of their win over Sporting Lisbon in Portugal.
If they fail to beat Fiorentina, one of those games could be played in the UEFA Cup Final week but scheduling both would be a sticking point with Bain.
Celtic have already made it abundantly clear they will formally object to any extension to the season.