Allied World Insurance Company is set to raise its bid for US reinsurer Transatlantic Holdings, according to a report in the New York Post.The move would turn up the heat in the battle with billionaire Warren Buffett’s Berkshire Hathaway and Bermuda reinsurer Validus Holdings in the fight for Transatlantic.Allied’s shares fell three percent, or $1.60, to $51.90 in New York Stock Exchange trading yesterday.The existing bid of the Bermuda Class of 2001 start-up, which moved its domicile to Switzerland last year, is valued at $2.9 billion, while the Validus bid is worth about $3 billion.Berkshire entered the race earlier this month when Mr Buffett tabled a $3.25 billion cash bid.The Post, however, reported that negotiations between Transatlantic and Berkshire may have ended. In a television interview, Mr Buffett said the negotiation period had “expired”, though Transatlantic has not confirmed this.The Post was unable to get comment from Allied or Transatlantic.