Norway and Iceland are both EEA members, effectively with one foot in the EU, Iceland was the first European country to sign such an agreement with China.
Norway and Iceland having free-trade with China while having deep access to the European single market leaves EU expansion in an odd situation. Neither country could become a full EU member without hurting trade with China, or alternatively the EU would have to make a similar FTA with China beforehand.
I've wondered what the realpolitik of the situation is. Is China's main interest in these deals to drive a wedge into further EU integration? Are they trying to create a situation where Norway and Iceland joining the EU would be contingent on the EU accepting a FTA with China?