Council chiefs in Edinburgh have reportedly requested further funding to ensure a tram line can be built from the city centre to the Granton waterfront.

Transport officials believe there will be enough money to provide a tram network from Leith to the airport by late 2010, with a spur from Haymarket to Granton one year later. But if they use up the £545m they already have, more cash will be needed to pay for the second line.

It is predicted that an extra 5,000 public transport passengers will travel southbound on Leith Walk between 2011 and 2031 in the two-hour morning peak period, leading to major bus congestion in the city centre unless trams are introduced.

It is also estimated that around £120m will have been spent on the tram project by the end of 2007.

Council leader Ewan Aitken said: "This really is the start of an exciting transport revolution and, in the future, I can envisage a more extensive tram network within the city and beyond. Phase two is closing the loop at the Waterfront and phase three is a link to Newbridge. Future ambitions include lines to the Edinburgh Royal Infirmary, Newcraighall, Livingston, Dalkeith, Musselburgh and Queensferry."

The councils finance director, Donald McGougan, said economic development in Granton and the surrounding areas would be accelerated as a result of a direct connection with central Edinburgh.