Beijing has included its South China Sea territorial claims on maps printed inside new Chinese passports, infuriating at least one of its neighbours.
Vietnam has made a formal complaint to Beijing about the new passports. "The Vietnamese side has taken note of this matter and the two sides are discussing it, but so far there has been no result," said Vietnam's embassy in Beijing.
Other countries that have clashed with China over its assertions in the South China Sea, in particular the Philippines, are also worried China is trying to force their immigration officials to implicitly recognise Chinese claims every time a Chinese citizen is given a visa or an entry or exit stamp in one of the new passports.
The Philippines embassy in Beijing has not responded to requests for comment.
The territorial disputes in the South and East China Seas have overshadowed a series of summits of Asia-Pacific leaders in Cambodia attended by US President Barack Obama this week, with discord among southeast Asian nations over how to respond to an increasingly assertive China.
China claims virtually the entire South China Sea, including large swaths of territory that smaller neighbouring countries say belongs to them, and Beijing has been increasingly strident in recent years in asserting those claims.
The claims are represented on Chinese maps by a "nine-dash line" that incorporates the entire South China Sea and hugs the coastline of the Philippines, Brunei, Malaysia, Vietnam and a small part of Indonesia.
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The nine dashes enclose a region that is believed to be rich in undersea energy reserves and also incorporate the self-ruled island of Taiwan, which Beijing claims as its territory. Until recently, most regional governments had assumed the nine-dash line represented Beijing's starting position for negotiations.
China undermined that view in June when CNOOC, a state oil company, invited foreign groups to tender for exploration rights in an area close to Vietnam's shoreline which Hanoi had already licensed to America's ExxonMobil and Russia's Gazprom.
The inclusion of the South China Sea claims and the nine dashes in the latest Chinese passport has raised further doubts about China's willingness to compromise on the issue.
"This is viewed as quite a serious escalation because China is issuing millions of these new passports and adult passports are valid for 10 years," said one senior Beijing-based diplomat who asked not to be identified because of the sensitivity of the issue. "If Beijing were to change its position later it would have to recall all those passports."
China's ministry of public security oversees the design and issuing of the new Chinese passports, according to an official at the Chinese foreign ministry who declined to comment further. As well as the controversial map, the passports also include pictures of scenic spots in China, as well as two popular tourist destinations on Taiwan.
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"The map on the Chinese passport is not directed at any specific country," the Chinese foreign ministry said in a statement to the FT on Wednesday. "China is willing to actively communicate with the relevant countries."
Since 2010 China has taken a far more strident stance on its territorial claims in the South China Sea, as well as in the East China Sea, where it claims the Japanese-administered Senkaku Islands, known as Diaoyu in Chinese, as its own territory.
The Japanese government has also paid close attention to the new Chinese passports but the scale of the map is so small that the islands are not visible and Tokyo has not raised the issue with Beijing, according to diplomats familiar with the matter.
The Chinese government began issuing the new passports, which include electronic chips for the first time, about five months ago.
"I think it's one very poisonous step by Beijing among their thousands of malevolent actions," said Nguyen Quang A, a former adviser to the Vietnamese government. "When Chinese people visit Vietnam we have to accept it and place a stamp on their passports . . . Everyone in the world must raise their voices now, not just the Vietnamese people."
Shi Yinhong, a professor of international affairs at Renmin University, said including China's territorial claims in the new passports could "demonstrate our national sovereignty but it could also make things more problematic and there is already more than enough trouble [between China and its neighbours over territorial claims in the South China Sea]". Prof Shi said it was likely that the decision to include the map was made at ministerial level rather than at the national leadership level.
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The Taiwanese government told the FT it had "noticed" the new passports but had not filed a formal complaint with Beijing.
"The mainland should face the reality of the Republic of China's existence and our established foundation," Taiwan's mainland affairs council said. "We should put aside disputes and face the reality and work together towards peaceful and stable development across the Taiwan Strait."
— Additional Reporting by Gu Yu in Beijing, Nguyen Phuong Linh in Hanoi and Sarah Mishkin in Taiwan.