US officials have expressed concern that an international court ruling expected in the coming weeks on a case brought by the Philippines against China over its South China Sea claims could prompt Beijing to declare an air-defense identification zone, or ADIZ, in the region, as it did in the East China Sea in 2013
Mr. Work told an event hosted by the Washington Post that the United States would not recognize such an exclusion zone in the South China Sea, just as it did not recognize the one China established in the East China Sea.
China claims most of the South China Sea, through which more than $5 trillion in global trade passes every year.
"We don't believe they have a basis in international law, and we've said over and over [that] we will fly, sail, and go wherever international law allows," Mr. Work said.
"We have spoken quite plainly to our Chinese counterparts and said that we think an ADIZ would be destabilizing. We would prefer that all of the claims in the South China Sea be handled through mediation and not force or coercion," he said.
Mr. Work spoke as Chinese President Xi Jinping prepared to visit Washington for a nuclear security summit this week.
The United States has accused China of raising tensions in the South China Sea by its apparent deployment of surface-to-air missiles on a disputed island, a move China has neither confirmed nor denied.
China, for its part, has repeatedly accused the United States of militarizing the South China Sea through its freedom of navigation patrols in the region and the expansion of military alliances with countries such as the Philippines.
In February, Chinese Foreign Minister Wang Yi said his country's South China Sea military deployments were no different from US deployments on Hawaii.
In a related development, Supreme Court Justice Antonio Carpio said on Thursday that if the United Nations Convention on the Law of the Sea (UNCLOS) fails to discipline China from violating international maritime laws, particularly in the disputed West Philippine Sea (South China Sea), it could lead to an arms race between the rival nations and their allies against China.
"[If the] UNCLOS cannot settle the most important maritime dispute today then it's useless. People will not go to avail themselves of the remedies under UNCLOS. They will just buy warships, warplanes and anti-ship missiles to defend their maritime zones," Mr. Carpio told journalists in a chance interview at Philippine National Police (PNP) General Headquarters in Camp Aguinaldo, Quezon City.
The UN international court at The Hague is expected to issue its verdict on the arbitration case filed by Manila against Beijing for the latter's aggressive actions at some maritime territories in the West Philippine Sea that are well within the Exclusive Economic Zone of the country as prescribed by UNCLOS.
Beijing has been using force and coercion against claimants of the disputed sea, and even went on a reclamation binge converting reefs and atolls into artificial islands for apparently military purposes banking on its controversial "nine-dash line" that effectively corrals in about 90% of the entire sea.
Beijing did not participate in the arbitration, and even repeatedly said it will not honor any verdict against her.
Beijing's behavior has been churning up regional tension that already drew international condemnation, and defense allies led by the United States have warned China of adverse repercussion.
However, Mr. Carpio believes Beijing doesn't want another world chaos if she believes in world order, peace and stability.
Mr. Carpio said he just can't think of a China wanting to own what is not hers and thereby creating tension with its neighbors by grabbing territories to the extent of violating agreements, such as the 1992 Code of Conduct of Parties, not to militarize the disputed sea and, worse, isolating herself by not adhering to international laws such as the UNCLOS.
"Well, this is the greatest threat to the Philippines since World War II, because a territory larger than our land area is being encroached on and seized from us by China," he said.
Other countries threatened by China's expansionist policy include Vietnam, Taiwan, Malaysia, and Brunei.
"If the nine-dash line is enforced by China, Vietnam will lose more than us because we still have the Pacific side; we have our EEZ on the Pacific side. Vietnam has no more; their back is to the land. So, once Vietnam loses its EEZ facing the South China Sea, they don't have an EEZ anymore. Same as Brunei," Mr. Carpio pointed out.
"Every country will have to defend its own maritime zones through warships and warplanes. It means resources that we need for education, for social services, for infrastructure, will have to be diverted to acquire military assets. Otherwise, we lose by default. So a lot of balancing has to be done, we have to strengthen our alliances because we cannot acquire assets overnight, it takes time," he said.