Leaders from the Group of Seven (G7) industrial nations meet on Sunday in the Bavarian Alps for a summit overshadowed by Greece's debt crisis and ongoing violence in Ukraine. Host Angela Merkel is hoping to secure commitments from her G7 guests to tackle global warming to build momentum in the run-up to a major United Nations climate summit in Paris in December. The German agenda also foresees discussions on global health issues, from Ebola to antibiotics and tropical diseases. But on the evening before the German chancellor welcomes the leaders of Britain, Canada, France, Italy, Japan and the United States, she and French President Francois Hollande were forced into their fourth emergency phone call in 10 days with Greek Prime Minister Alexis Tsipras to try to break a deadlock between Athens and its international creditors. The two sides have been wrangling for months over the terms of a cash-for-reform deal for Greece. Without aid from euro zone partners and the IMF, Greece could default on its loans within weeks, possibly forcing it out of the currency bloc. An upsurge of violence in eastern Ukraine will also play a prominent role at the meeting at Schloss Elmau, a luxury hotel perched in the picturesque mountains of southern Germany near the Austrian border. European monitors have blamed the bloodshed on Russian-backed separatists and the leaders could decide at the summit to send a strong message to President Vladimir Putin, who was frozen out of what used to be the G8 after Moscow's annexation of Crimea last year.