could you clarify this? are you saying that you want to pay for the hotel stay with amex points, AKA "membership rewards" points? or are you sayinjg on the amex travel website?

you should be able to pay charges to your card with points at 1cpp. a $100 charge would thus be 10,000 points. at least those are the rates here in canada. so you could book at marriott.com and use your amex to pay. when the charge appears on your account, you just use the "pay with points" feature.