中止异步Web服务调用并重定向到另一个URL（ASP.NET Ajax）

In my webapp, I have a list of links generated from code-behind and bound to a repeater control. Clicking on a link opens a popup window, where, along with displaying some data, an asynchronous call to a WCF Service is made (through a javascript proxy). This service in turn calls another third party web service that might take a long time to respond. I am working with IE6, thats a unavoidable requirement.In my webapp, I have a list of links generated