Chinese President Xi Jinping declared in May that China was willing to make its potential Covid-19 vaccines a “global public good” . It is a big promise, given that demand is huge and manufacturing vaccines is complex. But bargaining over vaccines has started appearing in China’s diplomacy playbook. Philippine President Rodrigo Duterte said on Monday last week that he had pleaded with Xi to give him priority access to a potential Chinese vaccine. A Chinese foreign ministry spokesperson said the next day that the request had been granted to “China’s friendly neighbour the Philippines”. The quick response highlighted Beijing’s geopolitical considerations as it aims to shore up relations with members of the Association of Southeast Asian Nations amid intensifying US-China tensions in the South China Sea . Beijing’s attempts at vaccine diplomacy has already extended to the United States’ backyard. It has pledged to provide a US$1 billion loan to Latin American and Caribbean countries to buy its vaccines – an extension of its engagement after it sent ventilators, protection gear and testing kits to the region in March. It has made similar pledges to Africa, Afghanistan, Pakistan and Nepal. On the other hand, China’s customs authority held up vaccine candidates being sent for trials in Canada, with which it has strained ties since the arrest of Huawei executive Meng Wanzhou . A recent internal briefing by Chen Wei, the scientist in charge of military vaccine research in collaboration with pharmaceutical firm CanSino, did not mention Canada, but said a third-phase trial was expected to start in other countries in August. If they pass human trials, most of the front runner vaccines will go to Western powers, especially the US and Britain, which secured supplies by investing heavily in the research. Smaller countries have to rely on a World Health Organisation (WHO) mechanism, Covax, or approach China directly. The WHO mechanism is designed to provide vaccines to cover 20 per cent of participant countries’ populations through self-financing and donations. China is not part of that mechanism, and fulfilling its own promises is a daunting task. It has been aggressively expanding its production capacity and is expected to partner with existing manufacturers for other vaccines. But meeting its domestic demand will be daunting enough, particularly because vaccines will probably require at least two doses. China managed to scale up production of protection kits for export, but vaccine diplomacy will be a lot more complex and difficult.