has until May 17 to file a response to the Japan Patent Office's rejection of its patent application for the "one-click" online-purchasing process.

Apple licensed "one-click" from Amazon last year for use on its Apple Store.

Last November, the Japan Patent Office notified Amazon that it had reason to reject Amazon's 1998 patent application, according to Kenichiro Natsumi, deputy director of the patent office's Technology Research Division. The agency sent a similar notification to Signature Financial Group concerning a 1992 application for a patent on its "hub and spoke" data-processing system.

Amazon must file by Thursday and sign by Monday, May 21. If either company fails to respond in time, the patent application will be rejected – although both can appeal against the decision.

In both cases, the patent office found "prior art" - evidence that others had the idea first. In the case of the "one-click" concept, the prior art consisted of an earlier Japanese patent application, and a 1996 book – User Interface Design by Alan Cooper.

"We decided that the technology could be easily invented from this prior art," Natsumi said in a phone interview yesterday.

Amazon's "one-click" system, patented in the US, enables repeat customers to place orders without re-entering personal information such as a credit card or address. Part of the patent covers the way Amazon stores its billing and shipping data. Amazon has faced criticism and legal challenges over the patent, which critics said could stifle innovation by other online merchants.

Earlier this year, the European Commission also decreed that Amazon's patent would not stand.