China began week-long military drills in the contested South China Sea on Tuesday, which will end on July 11, just a day before the Permanent Court of Arbitration (PCA) in the Hague rules in the territorial dispute over the region between China and the Philippines. Based on the coordinates provided on China Maritime Safety Administration’s website, an area of about 38,600 square miles has been cordoned off for the exercises.

According to reports, two guided missile destroyers, Shenyang and Ningbo, and a missile frigate, Chaozhou, were among the warships participating in the drill, which Chinese defense ministry officials said was “a routine exercise according to an annual plan.” All civilian ships have been told to stay out of the area, according to the notice specifying the coordinates.

“The timing of the exercises in the South China Sea is subtle, but it’s not necessary to link it with the arbitration, because the exercise is a routine activity that was planned a long time ago,” Liu Feng, an expert on Chinese maritime issues, told the Global Times on Sunday.

Ashley Townshend from the University of Sydney’s United States Studies Centre told the Guardian the exercises were both a response to the U.S. recently sending its navy ships to the region, as well as an attempt to show China’s resolve to the world ahead of PCA’s ruling. He added that there was also a strong domestic component to them.

“This show of force is about reassuring domestic audiences and demonstrating actions to meet the strong words that Chinese officials and Xi Jinping have come out saying [about the tribunal],” Townshend said.

Vietnam, which also has claims — competing with China — over Paracel Islands in the South China Sea, said Monday the military exercises seriously violate its sovereignty over the islands. “Vietnam strongly objects to the exercises and demands that China respect Vietnam’s sovereignty, behave in a responsible manner, and immediately end and refrain from taking actions that threaten maritime security and safety,” in the South China Sea, the country’s foreign ministry said.

The Philippines brought the case against China’s sweeping territorial claims in 2013, but Beijing has repeatedly said it would not abide by PCA’s ruling, calling the case “a farce” and the court’s arbitration a United States tool “to impose more pressure on China, causing more tensions in the South China Sea.”

According to reports, China has expressed willingness to negotiate the issues related to the contested region with the Philippines if Manila were to ignore PCA’s ruling. The talks would cover “issues such as joint development and cooperation in scientific research if the new government puts the tribunal’s ruling aside before returning to the table for talks.”

About $5 trillion of shipping trade passes through the resource-rich waters of South China Sea every year. Brunei, Malaysia and Taiwan are other countries that lay claim to the region.