Russian aggression against Ukraine a threat to world - Obama

BRISBANE Australia (Reuters) - The United States, as the world's only superpower, is leading the global community in opposing Russia's aggression against Ukraine, as well as other threats, U.S. President Barack Obama said on Saturday.

"We're leading in dealing with Ebola in West Africa and in opposing Russia's aggression against Ukraine, which is a threat to the world, as we saw in the appalling shoot-down of MH17," Obama said at a speech in the Australian city of Brisbane, where he is attending the Group of 20 Leaders Summit.