[German Chancellor Angela Merkel, center, takes her seat during a lunch with other leaders at an EU summit in Brussels on Monday, March 7, 2016. European Union leaders arrived in Brussels Monday to press Turkey to do more to stop migrants entering Europe and to shore up support for Greece, where thousands of people are stranded. (Olivier Hoslet, Pool Photo via AP)]BRUSSELS (AP) — European Union leaders on Monday pressed Turkey to take back thousands of migrants and prevent others from setting off for Europe as thousands of desperate people sat stranded in Greece.