relative clause or noun clause?

[wrongnumber]

The government banned Twitter in 2009 amid ethnic riots between Muslims and Han Chinese in Urumqi, the capital of Xinjiang, the western region where the government later started a mass detention and re-education campaign that the United States has declared a genocide.

Is this that a relative clause or a noun clause ?

source: New York Times, https://www.nytimes.com/2024/05/08/climate/china-us-podesta-liu.html

 

[5jj]

that the United States has declared a genocide is a relative clause.