Elmau, Germany, Sha'ban 21, 1436, Jun 8, 2015, SPA -- German Chancellor Angela Merkel and US President Barack Obama on Sunday called on the leaders of the world's major economies to take a tough stance against Russia over the conflict in Ukraine, according to dpa. "I'm assuming that we will send a united signal from here," Merkel told German public television ZDF during the Group of Seven (G7) summit in the Bavarian Alpine resort of Schloss Elmau. "Sanctions can only be lifted if the conditions under which they were imposed are no longer there and the problems have been solved," the chancellor said, echoing comments made by Obama during a private meeting with Merkel, according to the White House. The Group of Eight became the Group of Seven after Russia was expelled last year by the other powers. The United States and European Union also began imposing sanctions last year on Russian individuals and businesses over the annexation of Crimea from Ukraine. Merkel and Obama agreed that the "duration of sanctions should be clearly linked to Russia's full implementation of the Minsk agreements and respect for Ukraine's sovereignty," a White House statement said. Shortly after arriving in Germany for the summit, Obama said "standing up to Russian aggression in Ukraine" would form part of the talks. Fierce fighting between pro-Russian rebels and government forces has erupted again in recent days in eastern Ukraine, throwing into doubt the Minsk peace deal in February. European Council President Donald Tusk suggested that the EU could agree to a fresh round of sanctions, which are meant to punish Russia for what Kiev and the West say is Moscow's military backing of the rebels - an accusation the Kremlin has repeatedly denied. "If anyone wants to start a debate about changing the sanctions regime, the discussion could only be about strengthening it," he said at the G7 summit. In an interview published in the Italian newspaper Corriere della Sera at the weekend, Russian President Vladimir Putin repeated his view that the crisis in Ukraine was "deliberately" created by the West and that Russia "is simply forced to respond to what is happening." Merkel is chairing the summit of G7 states - which in addition to the US and Germany includes Britain, Canada, France, Italy and Japan. However, looming large over the gathering were concerns about the Greek debt crisis, with Athens urgently trying to reach a deal with creditors to unlock fresh bailout funds in exchange for tough reforms. Merkel and French President Francois Hollande held a tele-conference with Greek Prime Minister Alexis Tsipras on Saturday as pressure mounts on European leaders to head off the threat that Athens could soon run out of money and crash out of the eurozone. As relations between cash-strapped Greece and its European partners continued to worsen, Merkel stressed in her ZDF interview the need for all sides to work intensively to find a solution. "But we have also all made clear that in Europe solidarity on the one hand always go together with self-help on the other side. And we have still not reached that goal," she said. Speaking at a G7 press conference, European Commission President Jean-Claude Juncker also expressed his "disappointment" that Tsipras' failed to respond to a request to produce a new set of economic reform plans. EU diplomats said that time was running out in the negotiations but that the talks could not proceed until Greece presented the new proposals. Juncker's frustration with Greece underlined Athens' increasing isolation in Europe as it battles to reach a secure a deal. Until now, the commission president has been considered to be more sympathetic to Greece's arguments than other leading European figures. The Greek premier is to travel to Brussels on Wednesday for talks with European leaders. While the G7 leaders were meeting in Schloss Elmau, about 300 hundred anti-G7 protesters made an hours-long, 10 kilometre trek on mountain trails to the resort from the nearby town of Garmish-Partenkirchen only to be turned away by police when they reached the 3-metre-high fence surrounding the castle's grounds. --SPA 03:09 LOCAL TIME 00:09 GMT www.spa.gov.sa/w