Google has drawn up detailed plans for the closure of its Chinese search engine and is now "99.9 per cent" certain to go ahead as talks over censorship with the Chinese authorities have reached an apparent impasse, according to a person familiar with the company's thinking.

In a hardening of positions on both sides, the Chinese government also yesterday threw down a direct public challenge to the US search company, with a warning that it was not prepared to compromise on internet censorship to stop Google leaving.

The signs that Google was on the brink of closing Google.cn, its local search service in China, came two months after it promised to stop bowing to censorship there. But while a decision could be made very soon, the company is likely to take some time to follow through with the plan as it seeks an orderly closure and takes steps to protect local employees from retaliation by the authorities, the person familiar with its position said.