By Foo Yun Chee STRASBOURG (Reuters) - The European Union executive said on Tuesday that Greece has made progress in policing its part of the bloc's external border but more action was needed before emergency controls inside the free-travel zone can be lifted. The legal base for the temporary checks expires in May and the European Commission must decide whether Greece, overwhelmed by the arrival of more than a million people in the last year, has remedied the shortcomings. The Commission aims to restore the normal functioning of the Schengen zone of passport-free travel by the end of the year.