Animal campaigners say the pandas are being used as political pawns
Last minute negotiations are going on in China in the hope that Gordon Brown will be able to sign a deal to bring two Giant Pandas to Edinburgh Zoo.
However, Advocates for Animals have stepped up their campaign to block the deal saying the pandas are being used as "political and commercial pawns".
Earlier this year the Edinburgh Zoological Society signed a letter of intent with the Chinese Government.
The deal would see the pandas going to the zoo on loan for 10 years for a fee.
There are thought to be just 1,500 of the animals remaining and that number may be even less after the earthquake in China in May.
The zoo said it would be helping with a worldwide breeding programme to save the Giant Panda.
Iain Valentine, head of animals, education and conservation for the Royal Zoological Society of Scotland, said: "Giant pandas will be beneficial to Scotland and the UK in a number of ways but the society's primary concern is to participate in an international breeding and research programme to help secure the future of the species.
"We already care for a number of endangered Chinese species and we hope to establish long-term partnerships with conservation organisations in China that benefit these species and others that are currently threatened in the wild."
It was hoped the final details would be settled in time for Gordon Brown to sign off the agreement while he is at the Olympic closing ceremony in Beijing.
However, that now looks increasingly doubtful and Advocates for Animals has accused the zoo, and supporters of the scheme - including the Royal Bank of Scotland and the Scottish Government - of using the pandas as pawns in a diplomatic and commercial game.
Ross Minett, Advocates for Animals campaigns' director, said: "To learn that a pair of Giant Pandas may be used in this unethical manner reflects poorly on Scotland's reputation and the Scottish and UK Governments.
"If Edinburgh Zoo really wishes to help Giant Pandas, it should focus on supporting in situ conservation in Chinese panda reserves, along with preserving the animals' natural habitat.
"Giant Pandas must not end up behind bars in Edinburgh Zoo. It's not too late to put an end to this ludicrous plan."