The Scottish Government us being asked to back multimillion-pound plans for a rail link between Aberdeen International Airport and the city centre.
Local authority leader Jenny Laing has written to First Minister Nicola Sturgeon asking for support for the ambitious £70million project.
It would involve either a light or heavy railway and feature stations at the airport and the new Aberdeen Exhibition and Conference Centre.
It would also utilise part of the existing Aberdeen-Inverness line.
The city council believes it could be partly funded through the devolution of air passenger duty (APD).
Councillor Laing has told Ms Sturgeon that the duty collected from Aberdeen International Airport passengers is in the region of £21million per annum.
She has also told the first minister it would be “folly” not to include the rail scheme in the £250million City Region Deal jointly funded by the Scottish and UK governments.
But a spokeswoman for Economy Secretary Keith Brown said the council was now calling for a “blank cheque”.
She said: “We spent months working with representatives in Aberdeen and the north-east to agree the priorities for the £250million City Deal and for the additional, separate £254million investment from the Scottish Government.
“These include innovative projects to diversify the region’s economic base.
“Now Aberdeen council’s leader is looking for a blank cheque for a new initiative without putting forward a proper business case or feasibility study.
“We have made very clear our intention to cut APD to secure international connectivity and existing air routes while seeking to attract new ones to Scotland’s airports, including Aberdeen’s.
“We can see the potential such a competitive edge might give the north-east of Scotland’s economy – it is a shame that the Labour led council cannot.”