(AGI) Brisbane (Australia), Nov 15 - The United States, as theworld's only superpower, is leading the global community inopposing Russian aggression against Ukraine, U.S. PresidentBarack Obama said on Saturday. Addressing the G20 summit inBrisbane, also attended by Russian President Vladimir Putin,Obama said: "We're leading in opposing Russia's aggressionagainst Ukraine, which is a threat to the world, as we saw inthe appalling shoot-down of MH17." MH17 was the MalaysiaAirlines flight that crashed in July over eastern Ukraine with298 people aboard. . .