72-Hour Transit Visa-Free Hong Kong to Beijing

Hello,
I am traveling form the US to Singapore, then cruising from Singapore to Hong Kong. I have airlines tickets form HK to Beijing and less than 72 hours after I arrive in Beijing I have airlines tickets from Beijing back to the US. Does my travel itinerary qualify for the 72-Hour Transit Visa-Free?
Do I need have the airline declare this status on my behalf?
Thanks!