The United States and China have to lead the way in the fight against climate change, former US president Barack Obama said today. Speaking as the future of the landmark Paris climate accord hangs in the balance, he acknowledged differences with his successor Donald Trump but said the private sector also had a role to play. "It's important that big countries that are big emitters like the US and China. lead the way," he told a conference in the Italian city of Milan, saying developing countries were watching them. "The current administration has differences with my administration in terms of environmental policy," he said, referring to Trump. "The good news is the private sector has already made a determination that the future is clean energy. Those things are locked in now, into the energy sector." "Because of the debates taking place in the current administration the steps may be taken more slowly than they would have been done, but I'm confident," he added. Watch this also: [jwplayer o3Yxs7xZ] While campaigning last year, Trump called climate change a hoax perpetrated by China, and promised to cancel the deal if he won the presidency. Now, after months of uncertainty, he appears to be edging toward a decision on whether to honour the landmark 2015 agreement to limit global warming. A key White House meeting scheduled for Tuesday to discuss whether the United States will honour the Paris accord was postponed, with no new date set.