Supertram backers meet ministers for a 'key' meeting on 7 March

Kieran Preston, director-general of Metro, the West Yorkshire transport executive, issued the warning in a leaked letter to Leeds City Council.

Transport Secretary Alistair Darling is currently considering the �355m scheme.

Mr Preston says that without approval "in the next few weeks" the city council will lose its powers to compulsorily buy land for the project.

Costs slashed

The government suspended the project in July 2004 after costs spiralled to more than �500m.

A revised scheme revealed last November cut 4.5 miles from the proposed network, bringing costs close to the �355m originally pledged in 2001.

Metro wants the Department for Transport (DfT) to fund 75% of the costs.

In his leaked letter to city council leader Andrew Carter, Mr Preston says: "There are over 100 parcels of land yet to acquire and the purchase was put on ice when funding was revoked by Alistair Darling.

"My serious concern is that if we don't get the go-ahead soon, we will lose the land acquisition powers.

"This will mean millions of abortive expenditure and a delay of at least three years before we get back to being able to make a viable bid."

It is vital the revised proposal is carefully considered to make sure it offers value for money Department for Transport statement

In fact, such a delay would probably mean the entire project being dropped "by default", Mr Preston told BBC News.

The Leeds Supertram team will meet transport minister Tony McNulty on 7 March to press their case.

"That is a key meeting in terms of the whole future of the project," said Mr Preston.

"The DfT's officials have asked us 72 different questions about the revised case, they've written their report for the minister and it's now a question of getting a decision from him on 7 March."

A DfT spokesman said: "The Department has held detailed discussions with Leeds City Council and is aware of the timetable implications.