FARNBOROUGH, England—The director general of the European Space Agency said he has again broached the idea of inviting China to participate in the international space station project, despite continued strong opposition in the U.S. congress.

Johann-Dietrich Wörner said during an interview at the Farnborough air show that “we should really not close the door” on Chinese cooperation. He added that even though China is building its own space station, his recent talks with Beijing officials showed “that they are also still open...