By Samuel Shen and Aradhana Aravindan SHANGHAI/MUMBAI (Reuters) - Workers at a Cooper Tire and Rubber Co joint venture factory in China locked out their U.S. managers to protest against a $2.5 billion buyout by India's Apollo Tyres that they say will put their jobs at risk. Foreign managers could face the risk of "bodily injuries", Yue Chunxue, director of the labor union at Cooper Chengshan Tire Co in China's eastern Shandong province said. Apollo agreed to buy Cooper Tire in June in a debt-funded deal, sparking a three-month strike. "Unless the deal is canceled, we will continue to boycott it, to the very end," Yue said. No other details about the lock-out were immediately available, and it was not clear whether the American managers had tried to enter the factory. "It adds to the headache for sure, no doubt about that," said Harish HV, head of corporate finance practice at advisory Grant Thornton in India, which is not involved in the deal. "They (Apollo) will probably say they'll walk out of the deal and that it's for Cooper to figure out how to convince China (workers) and deliver the deal to them. I am sure they (Cooper) are interested in getting this deal done." Chengshan Group, the local partner in the joint venture, is also against the deal, Liu Shuhong, a legal representative at the Chinese company, said. Liu said the company had not been consulted on the acquisition. Last month, Chengshan filed a lawsuit against Cooper in a local court, seeking to dissolve the joint venture. Workers had returned to the factory from August 17 but continued to boycott work on Cooper-branded products, a statement from Chengshan said the union had said. Cooper shareholders will vote on the deal on September 30. Apollo says the combined company would get about 18 percent of its revenues from China. An Apollo spokesman was unavailable for comment, while Cooper could not be immediately reached for comment on Monday, a public holiday in the United States. (Additional reporting by Sumeet Chatterjee in MUMBAI and Mridhula Raghavan in BANGALORE; Editing by Louise Ireland)