President Trump said Saturday that he is “very surprised” about China’s alleged militarization of a string of islands in the South China Sea, which Secretary of Defense Jim Mattis reportedly said were used for “intimidation and coercion.”

The New York Times reported Saturday that Mattis, during a speech in Singapore, criticized the Chinese government’s placement of advanced military equipment and missiles in the South China Sea.

“Despite China’s claims to the contrary, the placement of these weapons systems is tied directly to military use for the purposes of intimidation and coercion,” Mattis reportedly said during a speech on Saturday at the annual Shangri-La Dialogue, a regional security conference.

On Saturday, the president tweeted: “Very surprised that China would be doing this?”

The president’s tweet comes after the White House announced the official U.S. delegation to China for a series of upcoming meetings slated to be held next week, following talks held in Beijing and Washington last month.

The talks will be focused on “rebalancing the bilateral economic relationship” between the U.S. and China.

White House Press Secretary Sarah Sanders also said in a statement that Secretary of Commerce Wilbur Ross will lead the discussions and will be joined by U.S. Ambassador to China Terry Branstad, Under Secretary of Treasury for International Affairs David Malpass, Under Secretary of Agriculture for Trade and Foreign Agricultural Affairs Ted McKinney, and U.S. Trade Representative Chief Agricultural Negotiator Ambassador Gregg Doud.

Additional officials from the Departments of Commerce, Treasury, Energy, Agriculture and the U.S. Trade Representative will also participate in the upcoming talks.

The meetings come following the Trump administration’s decision to slap tariffs on allies Canada, Mexico, and the European Union’s steel and aluminum shipments to the U.S. Trump has threatened tariffs on up to $150 billion in Chinese products to punish Beijing for pressuring U.S. companies to turn over technology in exchange for access to the Chinese market. China has vowed to retaliate with tariffs of its own.

The Associated Press contributed to this report.