A U.S. judge on Tuesday rejected Republican presidential candidate Donald Trump's pretrial bid to win a lawsuit brought by Trump University students who said they were defrauded into signing up for its real-estate seminars.

U.S. District Judge Gonzalo Curiel said in a written ruling that there was a "genuine issue of material fact" as to whether Trump knowingly participated in a scheme to defraud the students.

Curiel said there was extensive evidence Trump had not personally met, interviewed or selected Trump University instructors, though he represented they had been handpicked.

In a July 22 hearing, Curiel tentatively denied the bid by Trump to dismiss the lawsuit in California, one of three over the defunct Trump University venture.

Trump's lawyers had argued that the 2013 lawsuit in U.S. District Court for the Southern District of California should be dismissed because the New York real estate mogul, though personally involved in developing the concept and curriculum, relied on others to manage Trump University by the time the plaintiffs purchased seminars.

Trump's lawyers claimed that references in marketing materials to "secrets," "hand-picked" instructors or "university" were sales "puffery" and there was no evidence Trump intended to defraud students.

Follow CNBC International on Twitter and Facebook.

