When Barack Obama, US president, decided late last week to attend the final stages of the fortnight-long United Nations climate change conference in Copenhagen, which begins today, the gasp of relief from delegates heading to the Danish capital was almost audible.
Mr Obama's presence means a credible deal is much more likely because the leaders of almost all the world's big economies and emitters are now planning to attend the summit on the final day, when any agreement will be reached.
Wen Jiabao of China, Angela Merkel of Germany, Yukio Hatoyama of Japan, Manmohan Singh of India, Gordon Brown of Britain and Nicolas Sarkozy of France are among the more than 100 leaders who have confirmed their attendance.