What gauge of cable is advisable to connect to 12V sealed lead acid batteries in parallel?

I am building a small 70 Ah battery power supply (using AC inverter) by connecting two 12 volt sealed lead acid AGM 35 Ah batteries in parallel. The battery terminals will be less than 12 inches from each other. I'm not sure what gauge of cable is necessary or advised? Any advice on gauge and materials would be much appreciated.