Fortigate 60C/ Wan link load Balancing issue in showing interfaces.

Hello,

I have a Fortigate 60c with firmware v5.2.15,build766 (GA).I wanted to configure Wan link load Balancing but the problem is that

i can see only in interfaces DMZ and WAN2 .I wanted to use WAN1 and WAN2.

Has someone faced the same issue???Is there any resolution in this problem??

Regards.

Patrick.