Connect cable modem to DSL router.

I need to connect a router (no modem function) which is specified for use with DSL modem. I was planning on buying Asus RT-13U for the purpose.

The question is is there any way I can connect it to Motorola Surfboard cable modem provided by my ISP?

I have several cable/dsl combo wifi routers (eHome, D-Link, Belkin) but all are somewhat old and do infrequently drop connection to the cable modem.

Any help would be appreciated.