BRUSSELS (AP) — European Union leaders will grapple Thursday with one of the most divisive issues ever to face the 28-nation bloc; how to collectively share responsibility for the tens of thousands of people arriving on Europe's southern shores in search of a better life. Ahead of an EU summit in Brussels, fresh tensions have surfaced over the perceived need for national refugee quotas. So far, solidarity with front-line nations Greece and Italy, where the refugees land, has been limited. A mandatory quota scheme was opposed mainly by eastern European nations — the Czech Republic, Hungary, Poland and Slovakia.