US President Barack Obama and Canadian Prime Minister Stephen Harper have expressed hope that G-20 summit of the top economies of the world in Pittsburgh would be useful and productive. At a joint press conference along with Harper in Washington, Obama said both of them agree that coordination still needs to continue at the international level and they are looking forward to the G20, where both the countries can discuss how to sustain efforts to kickstart the economy. He said US and Canada would like to work out a sustainable growth model.br/