The Latest on preparations for Thursday's European Union summit (all times local):

2:50 p.m.

German Chancellor Angela Merkel says it makes no sense to talk about new quotas of migrants for European countries to take in when initial quotas agreed upon still haven't been divided among the EU.

Merkel said Tuesday instead her focus at an upcoming EU summit will be efforts to work with Turkey on reducing the flow of migrants to Europe in general.

Merkel says "I'll put all my energy into arguing this European-Turkish approach is the best way forward."

She says European countries have not yet divided up 160,000 asylum seekers as had been previously agreed so that it made no sense to discuss new quotas.

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2:35 p.m.

European Union chief Donald Tusk is making clear that the bloc's 28 leaders are heading into a summit this week that could fundamentally alter the political course of the continent.

Negotiations with Britain are still finely balanced over whether the EU can make the necessary reforms for Prime Minister David Cameron to support remaining an EU member in a national referendum on the issue.

At the same time, the migrant crisis is quickly turning into a seminal event, pitting east against west and many against Greece.

"The migratory crisis we are currently witnessing is testing our union to its limits," Tusk said as he sought compromise on both issues ahead of Thursday's summit.