By Alastair Macdonald STRASBOURG (Reuters) - European Commission President Jean-Claude Juncker urged EU governments on Wednesday to accept a mandatory system to share out a wave of refugees fleeing war and poverty but also promised to improve frontier defences and deport more illegal migrants. In his first State of the Union address to the European Parliament, Juncker outlined an emergency plan to distribute 160,000 refugees among the 28 EU member states and promised a permanent asylum mechanism to cope with future crises. Defending his much-criticised proposal for mandatory burden sharing, he said Europe could not leave Greece, Hungary and Italy, the main receiving countries, to cope with the flood.