ROME, Oct 31 (Reuters) - Leaders of the Group of 20 major economies made important progress in tackling the growing threat of global warming, Italian Prime Minister Mario Draghi said on Sunday, hailing the two-day summit a success. Draghi told reporters that for the first time all G20 nations had agreed on the importance of capping global warming at the 1.5 degrees Celsius level that scientists say is vital to avoid disaster. “We saw countries quite reluctant to move along the lines we were suggesting until few days ago, and then they moved,” Draghi said in a closing news conference, brushing aside criticism from climate activists that the G20 had not gone nearly far enough. “G20 leaders have made substantial commitments ... It is easy to suggest difficult things. It is very, very difficult to actually execute them,” he added. (Reporting by Gavin Jones and Angelo Amante; editing by Crispian Balmer)