Two student groups that plan to host conservative author Ann Coulter have sued the University of California at Berkeley, where she plans to speak.

Ms Coulter was due to speak on campus on 27 April, but after first abruptly cancelling the event, administrators chose to reschedule it for 2 May.

Young America's Foundation and the Berkeley College Republican said this violates their free speech.

The university started the so-called Free Speech Movement in 1964.

The Coulter event was cancelled by school administrators on 19 April over fears that protesters and counter-protesters would hold violent clashes on and off campus.

The lawsuit claims that Berkeley administrators are trying to "burden or ban" events "involving the expression of conservative viewpoints".

They say that the offer to reschedule the speech is "transparently insincere" since it is due to occur during a "dead week" when students are studying for final exams.

They ask the court to fine the school and award damages to the event organisers.

Ms Coulter still plans to visit campus on 27 April to discuss her 2015 book: Adios, America!: The Left's Plan to Turn Our Country Into a Third World Hellhole.

She tweeted a weather forecast for Thursday, saying "nice day for an outdoor speech".