U.S. Secretary of Defense Ashton Carter criticized China’s artificial island construction in the South China Sea, declaring that the United States would not be deterred by China’s military activity in the region.

The U.S. will remain the leading security power in the Pacific region for decades to come, added the Pentagon chief at the Shangri-La Dialogue in Singapore on Saturday.

John McCain (R-AZ), the chairman of the Senate Armed Services Committee (SASC), attached a provision to the 2016 National Defense Authorization Act (NDAA) that would provide up to $425 million over the next five years in military training and equipment to Southeast Asian nations facing territorial challenges from China.

China has been expanding its construction of a chain of artificial islands on submerged reefs and rocks in the South China Sea, an estimated 660 miles from its shores. The move has prompted territorial disputes.

“In the past 18 months, China has created 2,000 acres of new land in the ocean and constructed airstrips, hangars and ship berths,” reports Stars and Stripes. “Earlier this week, U.S. officials said that artillery vehicles similar to U.S. Howitzers were spotted at Fiery Cross Reef, where a Chinese dispatcher attempted to order a Navy P-8 Poseidon flying overhead to change course May 20.”

China has defended its rights and interests to build the artificial islands.

Speaking at the Shangri-La Dialogue in Singapore on Sunday, a day after Carter singled out China as a source of instability in the South China Sea region, Adm. Sun Jianguo said the construction of islands does not target any other nations or affect the freedom of navigation.

“I want to reaffirm that this construction is well within the scope of China’s sovereignty and it is justified, legitimate and reasonable,” said Sun, the deputy chief of General Staff Department of the People’s Liberation Army, reports state broadcaster CCTV.

“In spite of the sufficient historical and legal evidence and its indisputable claims of rights and interests, China has exercised enormous restraint, making positive contributions to peace and stability of the region and the world at large,” he added.

During the Shangri-La Dialogue on Sunday, the U.S. defense secretary toned down the rhetoric.

While he reiterated that China’s maritime construction work did pose a threat to security in the South China Sea region, he also noted that other claimant countries to the disputed territory were also at fault, reports The Economic Times.

Carter, speaking at the dialogue a day earlier, urged countries to focus on a peaceful resolution to the land reclamation friction in the region.

He asserted that the U.S. opposes “any further militarization of disputed features.”

“There should be an immediate and lasting halt to land reclamation by all claimants,” the secretary said, later adding, “There should be no mistake: the United States will fly, sail, and operate wherever international law allows, as U.S. forces do all over the world. America, alongside its allies and partners in the regional architecture, will not be deterred from exercising these rights – the rights of all nations.”

“Finally, with its actions in the South China Sea, China is out of step with both the international rules and norms that underscore the Asia-Pacific’s security architecture, and the regional consensus that favors diplomacy and opposes coercion,” also said Carter.

He acknowledged that China’s actions are bringing countries in the region together.

“The United States will always stand with its allies and partners. It’s important for the region to understand that America is gonna remain engaged…continue to stand up for international law and universal principles…and help provide security and stability in the Asia-Pacific for decades to come,” the Pentagon chief asserted.

Sen. McCain’s NDAA proposal would disburse nearly half a billion dollars over five years to provide military assistance to Indonesia, Malaysia, the Philippines, Thailand, and Vietnam in the form of “equipment, supplies, training, and small-scale military construction,” according to the Senate armed services panel’s version of the bill.

The SASC approved McCain’s provision on May 14 by a vote of 22 to 4, indicating strong bipartisan support.

Considered “must-pass” legislation, the 2016 NDAA still needs to clear the full Senate and House of Representatives, which is expected to vote on the final version of the bill later this year.