A Chinese boycott of the “World Cup of mathematics” this year could be decisive, according to a co-organiser of a petition calling for the event to be moved out of the United States this year.

Ila Varma, a University of Toronto mathematician and boycott co-organiser, said the country was “uniquely situated” to act – both as a target of US restrictions and as a major scientific powerhouse.

“The Chinese government does not apply sanctions to US universities the way the US government does to...