The extension of the Edinburgh Tram line to Newhaven is expected to cost more than £200 million, it has emerged.
Councillors will begin examining the final business case (FBC) after a special data room was opened at the city chambers on Friday.
The project was initially estimated at £165 million, with the FBC saying the extension can be delivered within a £196 million budget.
However recommended “optimism bias” of 6% takes this to £207.3 million.
A final decision will be made when the case goes to council on March 14 with journeys expected to begin in early 2023 after six months of testing.
Council leader Adam McVey said: “We need to invest in our capital city’s continued success and deal with the growth of our population in a sustainable way.
“Edinburgh has a fantastic public transport network but we need to extend tram to build on our first-class, fully-integrated transport system.
“As Scotland’s fastest growing city, things simply cannot continue as they are – the transport system must evolve to cater to a rapidly growing population.
“The Final Business Case before us now is the result of a huge amount of work by the project team to produce a strong business case for taking trams to Newhaven which – crucially – does not divert funding from other council services.”
Edinburgh City Council say the project would be funded through future tram fare revenues and a special dividend from Lothian Buses.
The public will be able to view the FBC in full after a transport and environment committee meeting on February 28.
Construction of the tramline began in 2007 and saw an eventual £776 million bill – more than double the sum earmarked at the outset.
The extension would provide a direct link from Newhaven and Leith to the city centre and out to Edinburgh Airport.
Mr McVey added: “Having developed the case further and gone through the tender process, we now have much greater certainty of the total project cost – following industry guidance, learning the lessons from the previous project and taking a thorough, diligent and prudent approach to risk management.
“We will work to make sure the timelines and costs in the final business case are met. All successful major infrastructure projects depend on extensive scrutiny and this major project is no different.
“All councillors will be taking the opportunity to examine in detail the FBC and associated documents in detail so that we can collectively make as informed a decision as possible come 14 March.
“If the council moves ahead with this project, we’ll be working hard to make sure we deliver this project on time, on budget.”