ROME/BRUSSELS (Reuters) - Leaders of the world's 20 largest economies are set to commit to supporting efforts to shorten to 100 days the period needed to develop new vaccines, drugs and tests in a pandemic, according to a draft joint document. In normal circumstances developing vaccines takes more than a decade, but the COVID-19 pandemic spurred an unprecedented rush in research, trials and regulatory procedures that made it possible to have vaccines ready in less than a year. Now G20 leaders want that period to be cut further. In health emergencies caused by pandemics we will support science to shorten the cycle for the development of safe and effective vaccines, therapeutics and diagnostics from 300 to 100 days, says a draft statement seen by Reuters that G20 leaders are set to adopt over the weekend at a summit in Rome. The draft is still subject to last-minute changes, but officials said that this commitment is expected to remain unchanged. (Reporting By jan Strupczewski and Francesco Guarascio tage)