The SPFL will hold crunch boardroom talks to decide the next step in their simmering sponsorship row with Rangers this week.
The Ibrox club are in dispute with league chiefs over Rangers' refusal to promote a £1.6million a year commercial tie-up with online car firm cinch.
Rangers chairman Douglas Park owns one of the biggest car dealerships in Scotland - and cinch branding was conspicuously absent from Ibrox as the champions opened the season with a 3-0 win over Livingston on Saturday.
In an email to clubs on Monday night, SPFL chairman Murdoch MacLennan branded the Rangers stance 'very disappointing'.
League sources have refused to speculate on potential sanctions if Rangers continue to breach 'fulfilment of rights obligations'. But MacLennan promised an update after board discussions this week.
'You will all be aware that earlier this summer the SPFL signed a title sponsorship contract with cinch,' he wrote. 'This contract is, by value, the biggest single sponsorship deal in the 131-year history of the league.
'In the context of what is, by any measure, a challenging economic environment, our Chief Executive and his commercial team deserve huge credit for delivering this deal.
'It is therefore very disappointing that one of our clubs has not felt able to deliver inventory to cinch.
'Your Board will be discussing this situation later this week. I will, of course, be in touch thereafter to give you a further update.' Rangers managing director Stewart Robertson was re-elected to the league board last month.
Relations are already strained with fellow board members after he was critical of league governance and what he claimed is the underselling of television rights.
The Ibrox chief is likely to field questions over growing concerns than cinch might tear up a deal which puts revenue into the coffers of all 42 clubs.