Taiwan does not believe China is sincere in offering it much needed COVID-19 vaccines and thinks it is working to prevent the island from getting shots for political reasons as infections surge, officials briefed on the matter told Reuters. China and Taiwan have exchanged barbs as the world fights the virus, worsening ties already at a low ebb because of Taiwan"s refusal to accept Chinese sovereignty and stepped up U.S. support for Taipei. The two have embarked on a bitter war of words about vaccines, much needed in Taiwan as the medical system comes under strain from new cases with only about 1% of the population of more than 23 million vaccinated. Taiwan says China blocked it from getting vaccines produced by Germany"s BioNTech (22UAy.DE), while China says it is happy to send a supply of that vaccine via its Chinese sales agent, Shanghai Fosun Pharmaceutical Group Co Ltd (600196.SS). But Taiwan will not take the vaccines from Fosun, saying there is a lack of transparency and that China refuses to provide relevant information. China"s Taiwan Affairs Office, which has repeatedly said its vaccine offer is sincere and Taiwan should not put up political roadblocks, said in a statement to Reuters that Taiwan"s allegation it was blocking a BioNTech deal were "nonsense". A senior Taiwan official familiar with the situation told Reuters that China had not used an existing channel to discuss medical issues, which has been used to exchange information on COVID cases, to address the vaccine question. Instead, he said, China was launching "political warfare" to "split and weaken" Taiwan, without a real intention to offer the vaccines. "They are shouting words like they really mean it but they won"t give it to you," he said. "There are certain procedures in Taiwan to import vaccines, and if their intention is real, they know what to do." The government had for months chosen not to publicise what it sees as Chinese intervention in the BioNTech case but had reached a point where it felt it had to, he added. "Vaccines are not politics. But mainland China knows the best in the world how to politicise vaccines." A security official looking into Chinese activity in Taiwan told Reuters that China was "making a lot of effort" to prevent Taiwan from getting vaccines. "It"s similar to dollar diplomacy. Just that now dollars are replaced by vaccines," he added, referring to accusations the two sides exchange over buying diplomatic support with loans and other inducements. China"s Taiwan Affairs Office repeated China"s stance that Taiwan had gone against commercial principles in seeking to bypass Fosun. "They clearly knew they were trying to keep going despite the task being impossible," it said. "LIAR" Taiwan"s Central Epidemic Command Centre said in a statement to Reuters that information about vaccines from Fosun in a state media report where the offer was made was "unclear" and there was no way to know if the shots complied with Taiwan"s regulations. Fosun has not responded to requests for comment. Taiwan"s government is also facing pressure at home from the main opposition Kuomintang (KMT) party to accept the Fosun vaccines. At a news conference on Thursday, senior KMT official Cheng Li-wun called President Tsai Ing-wen a "vaccine liar" and held up a sign saying people would die without vaccines. Cheng questioned why the government had refused to purchase vaccines from Fosun, saying their shots were "100%" BioNTech vaccines. "Everyone has purchased goods from a distributor before," she said, adding that Tsai was stuck on a "wall of ideology" and her rejection of China"s offer was to save face. Adding to Taiwan"s anger, this week it failed again in its bid to attend the WHO"s decision-making World Health Assembly as an observer, following objections from Beijing and its allies. Meanwhile, China"s almost daily incursions into the southwestern corner of Taiwan"s air defence zone have continued. On Tuesday, Hu Xijin, editor of China"s influential Global Times newspaper, said that while there were humanitarianism considerations on vaccines, Beijing still had a bottom line. "Military aircraft surrounding Taiwan and other pressure will continue," he said.