Leaders from the Group of Seven (G7) industrial nations backed a tough line towards Moscow at the start of a summit in the Bavarian Alps, with US President Barack Obama urging the gathering to stand up to Russian aggression in Ukraine.

Host Angela Merkel greeted Obama in the idyllic Alpine village of Kruen under blue skies, surrounded by locals in traditional dress, drinking beer and eating white sausage and pretzels.

The German Chancellor was hoping to secure commitments from her G7 guests to tackle global warming ahead of 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 the crises in Ukraine and Greece seemed likely to overshadow the discussions at Schloss Elmau, a luxury Alpine hotel near the Austrian border.

Obama said leaders would discuss the global economy, trade partnerships and “standing up to Russian aggression in Ukraine”, as well as threats from violent extremism and climate change.

Both he and Merkel highlighted the importance of the German-American relationship, damaged in recent years by revelations of US spying in Germany, including the bugging of the Chancellor’s mobile phone.

If anyone wants to start a discussion about changing the sanctions regime, it could only be about strengthening it

“My message to the German people is simple: We are grateful for your friendship, for your leadership,” said Obama, “We stand together as inseparable allies in Europe and around the world.” Merkel alluded to “differences” but described the US as “our friend” and an “essential partner”.

British Prime Minister David Cameron and European Council President Donald Tusk both said they hoped the G7 would present a united front on sanctions towards Russia.

Members of the G7 group attend the first working session of a summit at the Schloss Elmau hotel in Kruen, Germany, yesterday.

EU leaders agreed in March that sanctions imposed over Russia’s intervention in Ukraine would stay until the Minsk ceasefire agreement was fully implemented, effectively extending them to the end of the year, but a formal decision has yet to be taken.

Italian Prime Minister Matteo Renzi is known to be sceptical about sanctions and left-wing politicians in Germany have also called for them to be removed.

“If anyone wants to start a discussion about changing the sanctions regime, it could only be about strengthening it,” said Tusk.

European monitors have blamed a recent upsurge in violence in eastern Ukraine on Russian-backed separatists. Russian President Vladimir Putin was frozen out of what used to be the G8 after Moscow’s annexation of Crimea last year.

Leaders and reporters were shuttled to the summit site by helicopter yesterday morning as hundreds of protesters blocked the main road to Schloss Elmau. On Saturday, anti-G7 protesters marched in the nearby town of Garmisch-Partenkirchen. There were sporadic clashes with police and several marchers were taken to hospital with injuries, but the violence was minor compared to some previous summits.

Germany deployed 17,000 police around the former Winter Olympic games venue at the foot of Germany’s highest mountain, the Zugspitze. Another 2,000 were on stand-by across the border in Austria. In addition to climate and health issues, the leaders of Britain, Canada, France, Germany, Italy, Japan, the US and EU were due to discuss Islamist militant threats from groups such as Islamic State and Boko Haram.