Cannot update Symbol Links - Permission Denied

There's a symbolic link on my Linux machine which I want to update and point it to another location however I get permission denied error even though I have rwx permissions for the symbolic link:

$ ls -l /usr/bin/upgrades lrwxrwxrwx 1 root root 18 Feb 16 2015 /usr/bin/upgrades -> upgrade 

Here, /usr/bin/upgrades is a symbolic link to /usr/bin/upgrade which is a python script.

now, I want to point this symbolic link to another Python script in my home directory as shown below:

ln -sf test.py /usr/bin/upgrades ln: cannot remove ‘/usr/bin/upgrades’: Permission denied 

So, why do I get a permission denied error and also is there a way to update the symbolic link and point it to another location? I have rwx access to the symbolic link.

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