Media bosses at Warner Bros are growing impatient with actor Heath Ledger, following his continuing refusal to sign contractual terms to star in a potential sequel to this summer's The Dark Knight.

Ledger, who played iconic villain 'The Joker' in the latest Batman offering, has reportedly been approached no fewer than 19 times with regard to taking part in the franchise's third instalment.

"Between his failure to return calls and his complete lack of vocal input on the matter, I think we can safely assume it's a 'no'", said Warner Bros President Alan F. Horn.

Meanwhile, director Christopher Nolan says that, should a third Batman be made, he would love Ledger to return.

"Heath's performance in Dark Knight was mind-blowing. I just hope he comes out of his box at some point".

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