European leaders scrambled Thursday to break an impasse on giving Pakistan trade-linked aid and to convince Italian Prime Minister Silvio Berlusconi to unblock a trade pact with South Korea. Britain and Germany were pushing the 27-nation European Union at a summit in Brussels to offer Pakistan trade advantages to help the country battle flood devastation and fears of rising Islamist extremism. In a letter to EU partners, British Prime Minister David Cameron called for a concrete political commitment from the EU to Pakistan to enhance significantly its access to the EU market. The deal, however, faces a welter of obstacles, including concerns that it would be challenged at the World Trade Organization and fears in the European textile industry.