Reinsurer Validus Holdings Ltd (VR.N) on Sunday urged target Transatlantic Holdings Inc (TRH.N) to enter into discussions over its proposed takeover and said its offer is superior to one from Allied World Assurance Co (AWH.N).

Validus offered to buy Transatlantic earlier in July in a cash-and-stock deal worth about $3.5 billion at the time, trumping an all-stock bid by Allied World. While both bids are at a discount to Transatlantic's stock price, the Validus discount is smaller.

At one point, Transatlantic said Validus's offer could lead to a superior proposal, but the sides were unable to come to terms on a confidentiality agreement and Validus took its offer to shareholders.

Validus said on Sunday it delivered a letter to Transatlantic's board "to reiterate the superiority of its proposal".

It urged Transatlantic's directors to enter into discussions with Validus and said it would hold a conference call for stockholders and directors on Monday.

Transatlantic said last week that it had sued Validus in federal court in Delaware, alleging that it made "false and misleading statements" to shareholders.

Validus at the time called the lawsuit meritless, saying the action was expected and that it would pursue its tender offer.

Validus offered 1.5564 shares and a special dividend of $8 in cash for every Transatlantic share. Allied World offered 0.88 share of Allied World for each Transatlantic share.

Transatlantic's shares closed at $51.21 on Friday, Validus ended at $26.59 and Allied World finished at $54.45.

At those prices, Validus' offer is about $3.1 billion and Allied World's is roughly $3 billion, according to Reuters calculations.