Plink ssh script with multiple usernames

Hi

I am trying to SSH to a sonicwall to do backups of the device.

I can manually ssh and then run the command no problem but the issue is I cannot use plink to automate it.

When you ssh to the Sonicwall the first prompt is Login as: - here you can pretty much type anything you want and then press enter you get User: - here you enter the admin username and then you enter the password and your in.

if i do plink -ssh 1.2.3.4 -l admin -pw xyz  it uses admin for the first login but just sits then at the second login.

if I do admin@1.2.3.4 -l admin -pw xyz it does the same thing.

Is there any way to get around this issue.

thanks