Mondello Park has been forced to call off its Rallysprint test day on Sunday.
With Level 5 restrictions now back in force, the event, which replaced the annual Carlow Car Club Rallysprint, was well over-subscribed, but the Kildare track has now been forced to call a halt to what would have been a behind closed doors event.
Restrictions will be reviewed on 12 January, but there is a growing feeling that those restrictions could be even tougher by the middle of next month and are likely to be extended.
If that were to happen, the six-hour Fiesta team endurance race, which is due to run on Sunday 24 January, would also be in jeopardy.
The popular event, which has attracted some of the biggest names in Irish motorsport down the years, has already been postponed twice and in January due to see the inclusion of the former BTCC title winner Andrew Jordan who won the series in 2013.