A conservation charity and park authority aim to raise £2m still needed to rescue plans for a Snowdon cafe once labelled a "slum" by Prince Charles.
The deadline for raising the £2m is the end of June
The 70-year-old cafe at the summit is deteriorating, but there are doubts over funding for a new building.
A worldwide appeal was launched last week to secure the £9m project.
The Snowdonia National Park Authority said it would be working with the Snowdonia Society to meet the June deadline to secure funding.
Plans were approved more than a year ago for a stone and glass building, designed to blend in with the landscape.
It would replace the existing concrete block housing the cafe and mountain railway station.
Snowdonia National Park Authority Chairman Caerwyn Roberts said they were "absolutely determined" that the new building would go ahead.
He said: "Although we have been successful in raising nearly 75% of the total project, the shortfall of £2m has to be raised urgently."
"We're a very small authority and our day-to-day work with conservation, planning and visitor enjoyment continues.
"We therefore have an enormous task ahead of us and we are very grateful not only for Snowdonia Society's support, but we are also extremely indebted for their help in administering this fund".
The Snowdonia Society, which was set up in 1967, is a voluntary conservation charity working to protect the national park.
Unless the £2m is secured by the end of June the whole financial package collapses.
The run-down current café is nearly 70 years old
It is estimated that 350,000 visitors make the trek to the top of Wales' highest mountain every year by train or on foot.
Last October Environment Minister Carwyn Jones confirmed a £3m injection from the assembly government towards the project.
More than £1m has also been secured by grants from the Wales Tourist Board, Welsh Development Agency and Snowdon Mountain Railway.
But financial advisers have said it would be difficult to raise even half the £2m needed.
The Snowdonia Society has called the new cafe "essential for tourism and development of all sorts in north Wales".
Dan James, the society's operations director, said: "This is a major project which will greatly enhance one of the best known mountains in the UK."