The Obama administration sought Tuesday to increase pressure on Europe to brand Hezbollah a terrorist group after the Bulgarian government implicated the militants in a fatal attack on Israeli tourists last summer.Bulgaria blamed the Iran-backed group for the July bus bombing in the Black Sea city of Burgas, making official what U.S. and Israeli terrorism officials had alleged from the start. The attack killed five Israelis and their Bulgarian driver.Bulgaria said evidence showed that two of the people involved in the attack were members of Hezbollah’s military wing and that they were acting as part of a campaign against Israeli targets worldwide. The United States and Israel assisted with the investigation.The allegation of a direct Hezbollah terror campaign on European soil escalates pressure on the European Union to reconsider its treatment of Hezbollah. The E.U. has resisted past U.S. and Israeli entreaties to designate Hezbollah a terrorist group. Secretary of State John F. Kerry issued a statement urging Europe to crack down on Hezbollah. "We need to send an unequivocal message to this terrorist group that it can no longer engage in despicable actions with impunity,” said Kerry.Several influential members of the 27-nation E.U. alliance have argued, however, that Hezbollah is both a political and military organisation and that a blanket terrorism designation could be counterproductive. Hezbollah supporters move through Europe and raise money with little obstacle.Agencies