GENEVA, Sept 28 (Reuters) - The head of the World Health Organization said on Tuesday that he expected all countries, including China, to collaborate in the second phase of a probe into the origins of the coronavirus after an initial mission to China. Speaking at a Geneva-based event on trade and COVID-19, WHO director-general Tedros Adhanom Ghebreyesus said that he hoped that the next phase of studies would begin as soon as possible. He also repeated his support for an international treaty on pandemic preparedness and response. "The world needs a framework," he said.