In a letter to workers, it said continued Brexit uncertainty is not helping firms to "plan for the future".
In 2016, the carmaker said it would build the new model in the UK after "assurances" from the government.
Unions described the news as "disappointing" and said they were "seriously concerned".
The government said Nissan's decision was "a blow to the sector" but that no jobs would go as a result.
Nissan has made cars at Sunderland since 1986 and employs almost 7,000 people.