Dundee United fans have been given an April 1 deadline to snap up their tickets for Ibrox in order to increase the allocation.
Only a sell-out of the Broomloan Stand tickets by that day will force the SFA to free up more spilling into the Govan Stand for the William Hill semi-final clash against Rangers on April 12.
Commenting on the ultimatum, Tannadice director Derek Robertson said: “It is not the ideal solution but not uncommon.
“What is important is that every single United fan who wants to attend this game and support the team is now in a better position do so.
“That is why I encourage each and every fan to act swiftly and secure their ticket at the earliest possible opportunity.
“The club fully appreciates that the deadline date of April 1 is a potential problem for some, but we have been advised that should we not sell our initial allocation by this date, no further allocation will be forthcoming.
“This is a fabulous opportunity to reach the Scottish Cup final so ensure your ticket, get behind the team on the day and do your bit to help achieve glory!”
Sales start this Monday at 10am to season ticket holders on a reserve basis with actual deliveries not arriving at the shop until next Thursday at the earliest.
Voucher C will be required to secure an order although there will not be a restriction on the number of tickets to be purchased.
Prices for the initial allocation are £15 for adults and £5 concessions (under-16, over-65 and students).
Further details on the club website at www.dundeeunitedfc.co.uk.