The bill for reopening an old railway line has doubled to nearly £60m, but work will still go ahead next month.
The project is still on track despite the increased cost
The cabinet earmarked £30m two years ago for reviving the 13-mile track between Stirling, Alloa and the Longannet power station in Kincardine.
Ministers said they would give the green light to the project because of the perceived benefits to adjoining communities.
The link - due for completion in 2007 - will carry passengers, but also coal.
Opponents in the village of Clackmannan complained in 2003 that the route would be dangerous and affect their property prices.
But supporters have argued it would lead to less congestion on the Forth Bridge and make Alloa and the surrounding area more accessible to commuters and business.
The scheme has been hailed as one of the most important rail projects in Scotland for decades.
A new station would be built in Alloa, allowing direct hourly passenger services to Stirling and Glasgow Queen Street.
The price rise has been blamed on inflation, increased charges by Network Rail, higher compensation for landowners and the extra cost of stabilisation work.
But Transport Minister Tavish Scott, who claimed that lessons had been learned, has now said he could find the extra cash from his coffers.
"The rise in costs will not affect funding for any of our other major projects and will be met from our existing budget," he said.
"We should be celebrating that construction work can now start and welcoming the hard work done by all those involved in the project."
The green light was welcomed by Clackmannanshire Council head Keir Bloomer.
"This is a historic occasion and we are delighted that all the funding for the completion of the railway is now in place," he said.
"A key objective of this council in terms of the economic regeneration of the area - the reopening of the rail line - will be a tremendous boost to the communities involved."