Google on Wednesday pulled out of a seach-advertsing deal with Yahoo, citing opposition from antitrust regulators and advertisers. The U.S. Justice Department said in a statement that it had told Google it planned to file a lawsuit to block the deal on antitrust grounds. Yahoo was baffled at Google’s decision, saying it was “disappointed that Google had elected to withdraw from the agreement rather than defend it in court.” Google and Yahoo, the Nos. 1 and 2 in the Internet search market, announced the deal in June. Between them, they have more than 80% of the Web search market, per comScore.