Defendants in a $2 billion lawsuit involving three billionaires—two Russians and an American who emigrated from Russia—said in a new filing that the legal action should be dismissed after the plaintiff in the case allegedly perjured himself.

Attorneys for defendants Len Blavatnik and Viktor Vekselberg said in the filing that Leonid Lebedev, another billionaire and former Russian politician, has been lying about his relationship with a company at the center of the lawsuit since it was filed in 2014.