Confronted with dwindling fuel reserves; a B747-400 Captain was forced to declare an emergency and invoke Captain's authority to proceed to an airport of his choosing when ZBAA Approach refused to clear them to either their filed alternate or other suitable airports.

Narrative

Upon our arrival in the Beijing terminal area we were given a hold at a fix named KR due to a developing thunderstorm. Beijing Approach informed us there would be a two hour delay before we could land in PEK. The Captain informed Beijing approach that if the delay was actually going to last 2 hours we would need to go to our alternate. Beijing Approach then updated the delay to at least one hour. We had approximately 30 minutes of hold fuel at that time.The Captain asked Beijing Approach for a clearance to Tianjin ZBTJ; our flight planned alternate. Approach asked us to pick another alternate. They would not clear us to ZBTJ nor would they give us a reason why we could not proceed to our flight planned alternate. During this process we were in contact with Dispatch and informed him that we were having problems getting a clearance to our planned alternate. The Dispatcher forwarded all the possible alternates; weather forecasts and landing data. After reviewing the choices and consulting with Dispatch; ZBSJ and ZBYN were chosen as suitable alternates. The Captain then asked Approach for clearance to either ZBSJ or ZBYN and was denied clearance and asked to choose another airport. With no other suitable alternates within our fuel range; the Captain declared an emergency for fuel and asked for a clearance to Beijing and was again denied clearance. The Captain; exercising Captain's emergency authority; asked for and received a clearance to ZBYN and performed an uneventful landing.