Validus Reinsurance Ltd’s financial strength rating of A- (excellent) and issuer credit rating (ICR) of “a-” remain unchanged by AM Best Co following its parent company Validus Holdings Ltd’s unsolicited bid for Transatlantic Holdings Inc, the ratings agency announced yesterday.Best also maintained the ICR of “bbb-” and the indicative ratings of “bbb-”, “bb+” and “bb” of senior debt, subordinated debt and preferred stock shelf registration, respectively, of Validus Holdings.Presently, all of the ratings have a positive outlook.Validus Holdings, which acquired IPC Holdings Ltd in 2009, on Tuesday put in a counter offer worth $3.5 billion to acquire Transatlantic Holdings after the takeover target agreed to merge with Allied World Assurance Company Holdings AG in a deal valued at about $3.2 billion.While Best believes the proposed transaction would be material to Validus, it said that there were no rating implications currently resulting from the offer itself.