China is considering suing people suspected of committing economic crimes who have fled to the United States and elsewhere with billions of dollars, an unusual step in a widening anti-graft campaign, a senior official said on Wednesday.

The move, part of President Xi Jinping's anti-corruption drive, underscores the challenges China faces in seeking the return of so-called economic fugitives.

Xu Hong, director general of the Foreign Ministry's Department of Treaty and Law, said China tried to persuade the United States to sign an extradition treaty, but Washington said it was "not ready."