The Czech prime minister told a summit of 15 European leaders Friday that a planned missile defense system, parts of which the United States wants to base in the Czech Republic and Poland, is vital to Europe's security. «The defense of Europe against missiles from some states and organizations is a necessary step which will significantly increase our security and also the security of our European allies and neighbors,» The Associated Press quoted Mirek Topolanek as tolding the annual gathering of presidents from central, southern and eastern Europe.