The board of Transatlantic Holdings has not accepted the takeover proposal by Berkshire Hathaway owned (re)insurer National Indemnity, but left the door open for further discussions.

The board said in a statement that the $52 per share offer “does not constitute a superior proposal,” but legally, the board must offer to engage in discussions and information exchanges with National Indemnity.

As with Validus' offer in mid-July, the board said the discussions are “reasonably likely” to lead to a superior proposal.

National Indemnity’s offer values Transatlantic at $3.25bn. Validus’s offer of 1.5564 Validus shares plus $8 in cash per Transatlantic share valued Transatlantic at $2.9bn as of 5 August, while Allied World’s offer of 0.88 Allied World shares per Transatlantic share valued the company at $2.76bn as of the same date.

Transatlantic's book value a share at 30 June 2011 was $67.76, meaning that all three offers are a discount. Allied World's bid valued Transatlantic at $44.22 a share on 5 August, Validus's $46.37 and National Indemnity's $52.