Teva Pharmaceutical Industries Ltd (TEVA.TA) is preparing to raise its bid for rival drugmaker Mylan NV (MYL.O) by as much as $2 billion, to $43 billion, Bloomberg reported on Monday, citing people familiar with the matter.

The improved proposal could be announced as soon as this week, Bloomberg said.

Teva may offer $86 to $88 per share for Mylan, up from the $82 per share it bid in April, Bloomberg reported.

Mylan rebuffed Teva's $40 billion bid in April, saying it grossly undervalued the company, and pressed on with its own $34 billion hostile bid for Perrigo Co Plc (PRGO.N) in an attempt to fend off Teva's interest.

Mylan's market value stood at $34.36 billion as of Thursday's close, according to Thomson Reuters calculations.

Mylan was not immediately available for comment and Teva declined to comment.