adding %post_id% to the permalink structure makes blog not to function

im having a strange problem setting up permalinks in my blog.

in the permalink settings i tried to change the permalinks to a format where i can have the post name and the post id in the url so i set the below structure

/blog/%postname%/%post_id%

but unfortunately when the above setting is in place my blog doesnt load at all, instead it gives a error in firefox

The page isn’t redirecting properly

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

when i use `/blog/%postname%/ it works the problem comes when i try to add the post id to the structure.

can someone please tell how how can i fix this error?