Roche has once extended its $5.70 billion hostile bid for US gene decoder Illumina, giving no sign that it intends to raise its offer.

In February, the Swiss major extended its $44.50 per share offer to March 23, and now that period has expired. Hardly any shares have been tendered so the date has been pushed back the date again to April 20.

That is two days after Illumina's annual meeting to be held on April 18, where Roche is trying to get its own slate of directors elected to the board. Last week, Roche chief executive Severin Schwan criticised Illumina's management, saying its "inactivity" in agreeing a deal is hurting the company's shareholders.

However, the board is not impressed and after the offer was extended again, said that it "continues to believe that Roche's offer is grossly inadequate". It adds that "Illumina is positioned to create far more value than Roche has offered. Our stockholders clearly agree".

While analysts believe Roche will indeed up its bid, the healthcare giant has history in not rushing in these matters. This waiting approach has been successful in the past, resulting in the acquisition of US diagnostics company Ventana Medical Systems in 2008 and the buy-out of Genentech a year later.