The cost of policing the UN climate change conference in Glasgow has been estimated at around £250m.
This is an “indicative” figure detailed in a paper which will go before the Scottish Police Authority on Wednesday.
The paper also references specific concerns about COP26 and the political tension between Holyrood and Westminster.
It confirms that Police Scotland “remains concerned about the current lack of governance coordination between governments, and the lack of clarity on agreed outcomes for this event”.
About 30,000 people, including 200 world leaders, are expected to attend COP26 in November.
Police Scotland will draft in officers from across the country for the summit under mutual aid arrangements, making it the largest mobilisation of police officers in the UK.
In comparison to other major events, the cost of policing the 2005 G8 summit at Gleneagles was £72m while the security bill for the 2014 Glasgow Commonwealth Games was £90m.
The COP26 paper states: “The UK government have been advised of the indicative policing costs which are estimated to be £250m.
“The UK government have been provided with a high-level breakdown of these costs which are presented on the basis that there will be no financial detriment to the Scottish policing budget.
“In the absence of assured planning assumptions, these figures are based on reasonable worst-case scenario assumptions and will remain indicative and will be subject to internal validation and independent security and financial assurance work between now and March 2020.”
Scottish ministers have previously said they expected the UK government to cover the “core costs” including emergency services funding.
Last week, First Minister Nicola Sturgeon insisted the summit would not cause “squabbles” between the Scottish and UK governments.
In a speech to a think tank in London, Sturgeon said her government would work “closely and constructively” with its UK counterparts.
Her comments came after Claire O’Neill, who had been coordinating plans for the summit, was controversially sacked by Downing Street.
A role reportedly turned down by former Conservative heavyweights David Cameron and William Hague, the COP26 presidency had been in a state of limbo until the announcement last week that business and energy secretary Alok Sharma would take up the challenging post.
The full financial implications of COP26 are now set to be reported as a standing item to the SPA Resources Committee this week by event gold commander, assistant chief constable Bernard Higgins.
The financial implications of policing COP26 will then be discussed at the Justice Sub Committee on February 20.
The UK Government has previously said discussions with the Scottish Government on the conference costs are “currently ongoing”.