Bermuda-based reinsurer Validus Holdings Ltd continued the verbal tit-for-tat surrounding its efforts to take over US reinsurer Transatlantic Holdings Ltd.Last week Validus put in an offer intended to derail a previously announced merger agreement between Allied World Assurance Company and Transatlantic, announced last month.On Tuesday, Transatlantic said its board remained committed to the Allied World deal, that it did not consider Validus' offer to be superior, but that it would seek an improved offer.Yesterday Validus insisted its offer was superior."Validus has delivered to the board of directors of Transatlantic a superior proposal that provides a 27.1 percent premium to the June 10, 2011 Transatlantic unaffected share price of $44.01, and a 5.3 percent ($2.63 per Transatlantic share) premium to the current implied value of the Allied World transaction," a Validus statement said."In contrast, the implied value of Allied World's offer currently represents a 4.3 percent discount to the Transatlantic share price."Validus is pleased that the Transatlantic board has offered to engage in discussions and exchange information with Validus, and the company looks forward to the opportunity to speak with Transatlantic and exchange information regarding Validus' superior proposal."