By Jeremy Page in Beijing and James T. Areddy in Shanghai 
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China on Sunday outlined in detail for the first time its objections to a U.N. tribunal on its territorial dispute with the Philippines in the South China Sea, and called again for bilateral talks to resolve a standoff that has heightened tensions in the region. 

A lengthy position paper published by China’s foreign ministry said it aims to explain why Beijing believes the tribunal lacks jurisdiction over the dispute, and reiterates that China “will neither accept nor participate in the arbitration” initiated by the Philippines in January 2013. It said that in pursuing arbitration Manila was going back on previous understandings to settle differences bilaterally. 

The Permanent Court of Arbitration in The Hague has given Beijing until Dec. 15 to file its response to the Philippines’ own 4,000-page submission, which argues that the Chinese claim to most of the South China Sea has no legal basis. 

Philippine Department of Foreign Affairs spokesman Charles Jose said the Philippine government is studying China’s position paper. 

The case is a rare example of a neighbor challenging China’s territorial claims through international arbitration. It is being closely watched by other nations, including the U.S., which has a defense treaty with the Philippines and has backed its legal challenge. 

Tensions in the region have mounted in recent years as Chinese ships and planes have repeatedly confronted vessels from the U.S. and its allies in disputed areas of the South China Sea and in the East China Sea, where Beijing and Tokyo have overlapping claims. 

Underscoring Beijing’s refusal to take part in the arbitration, a senior Foreign Ministry official told a news conference on Sunday that the position paper wasn’t a response to the tribunal, and the timing of its release wasn’t linked to the Dec. 15 deadline. 

Instead, the Chinese government wanted to provide a more detailed legal explanation of its position, which had taken some time to prepare, said Xu Hong, director general of the ministry’s Department of Treaty and Law. 

“Some people, who do not know the truth, have questioned China’s position of not accepting or participating in the arbitration,” Mr. Xu told the news conference. 

“No acceptance by China is signified in this position paper of the views or claims advanced by the Philippines,” he said. “China urges the Philippines to return to the right track of resolving the dispute through negotiation as soon as possible.” 

The Philippines accuses China of taking unilateral and provocative steps–especially in the last three years–to assert territorial claims in the South China Sea, such as by constructing structures on islands claimed by Beijing and Manila. 

The U.S. has also accused Beijing of using increasingly coercive methods and threatening freedom of navigation in the area. Still, Washington says it doesn’t take sides on the territorial disputes, which also involve Malaysia, Vietnam, Indonesia, Brunei and Taiwan. 

China says it is simply responding to unilateral moves by the Philippines and Vietnam to bolster their claims, and accuses the U.S. of interfering in the territorial disputes to counteract Beijing’s expanding influence in the region. 

Although Beijing has made it clear that it won’t observe the tribunal’s verdict, analysts and U.S. officials say the case could nonetheless help to clarify the legality of China’s claims, which are demarcated by a U-shaped “nine-dash line” covering almost all of the South China Sea. 

China’s position paper didn’t make fresh territorial claims or alter its basic stance on the issue, but reiterated its “indisputable sovereignty” over the particular islands and related waters disputed with the Philippines. 

Mr. Xu, the Foreign Ministry official, said that there had been no bilateral negotiations on the issue with Manila, despite what he said were Philippines’ claims to the contrary. 

The Philippines’ complaint against China comes under the United Nations Convention of the Law of the Sea, or Unclos, which both countries have ratified. 

China’s position paper said the arbitration represented an “abuse” by the Philippines of the convention’s dispute-settlement procedures. Besides, it said, China had formally declared in 2006 that it wouldn’t take part in those procedures on sovereignty issues. 

“The unilateral initiation of the present arbitration by the Philippines will not change the history and fact of China’ s sovereignty over the South China Sea Islands and the adjacent waters,” the paper said. 

Cris Larano in Manila contributed to this article.