Hungary's Central European University, a graduate school founded by US financier George Soros, said it was being forced out of the country by the nationalist government and would switch to enrolling new students in Vienna if it did not get guarantees of academic freedom by Dec. 1.

The US billionaire, who promotes liberal causes through his charities, has been the subject of a campaign by the right-wing government of Prime Minister Viktor Orban. Earlier this year, his charitable Open Society Foundations was forced to leave Hungary.

Thursday's move by CEU, which was quickly dismissed as a "political ploy" by the government, could deepen a rift between Orban and the European Commission, which has challenged his higher education reforms in the European Court of Justice.

A change last year to national law on education which withdrew the right to operate from foreign-registered universities that did not also offer courses in their home country was widely seen as explicitly targeting CEU.

The CEU offers graduate-level courses taught in English and is frequently ranked as the top university in Hungary. The prospect last year that it might be driven from Hungary drew street protests and international criticism.

The university's statement on Thursday said the Orban government had kept it in legal limbo for more than a year by failing to reach a formal agreement on its status.