IPSEC tunnel backup for point to point link

I have created a IKEv2 sit to site tunnel between fortigates using loopback addresses on Port 1. I also have a 10Gbps point to point link between two sites on port12 which is used a primary connection. I want to use Ipsec tunnel as a backup connection so that if point to point link is failed all ip traffic is switched over IPSec tunnel. 

Following is my config. Can some one suggest a solution for this scenario. 

set name "Traffic_for_loopback_IPSEC"

    set uuid f5a16342-7b79-51ef-6e44-02c65af6bb78

    set srcintf "loopback_FG1" "port1"

    set dstintf "loopback_FG1" "port1"

    set action accept

    set srcaddr "h-10.10.11.1-32" "h-10.10.9.1-32"

    set dstaddr "h-10.10.9.1-32" "h-10.10.11.1-32"

    set schedule "always"

    set service "ESP" "IKE"

 edit "IPsec_to_FG2"
        set interface "loopback_FG1"
        set ike-version 2
        set peertype any
        set net-device disable

     set proposal aes128-sha256 
     set remote-gw 10.10.11.1
     set psksecret XXXX

    next
end