U.S. President Barack Obama delivers remarks after meeting with the Philippines President Benigno Aquino alongside the APEC summit in Manila, Philippines, Nov. 18, 2015. Reuters

U.S. President Barack Obama said China should stop expansionist activities in the South China Sea a day after he announced the U.S. was giving the Southeast Asian country two more ships to help defend its borders. Obama made the remarks after a meeting with Philippine President Benigno Aquino as the Asia-Pacific Economic Cooperation (APEC) summit got underway in Manila on Wednesday. Chinese President Xi Jinping is also at the summit.

In the past year, China has exercised its claim to owning most of the South China Sea by building artificial islands with airstrips and other facilities in areas claimed by the Philippines. In June, it also brought back an oil rig to an area claimed by Vietnam, after withdrawing it for a year.

"We discussed the impact of China's land reclamation on regional stability," Obama told reporters after the meeting. “We agree on the need for bold steps to lower tensions, including pledging to halt further reclamation, new construction, and militarization of disputed areas in the South China Sea."

Last month, the U.S. sent a Navy ship close to one of those islands, within the 12-mile radius China claims, and said it would send ships as often as twice per quarter as part of what it calls its freedom of navigation program. Days after that, a court in the Hague said it had jurisdiction over a Philippines-China dispute over one area; China doesn’t accept the jurisdiction.

"As President Aquino indicated, disputes need to be resolved peacefully," Obama said. "That is why the U.S. supports the Philippines' decision to use arbitration under the U.N. Convention of the Law of the Sea to peacefully and lawfully address differences."

The U.S. is giving the Philippines a cutter and a research vessel. A frigate it gave in 2011 already figured in a standoff with the Chinese navy in 2012.

In a speech at the APEC CEO Summit earlier Wednesday, Xi did not discuss the South China Sea, focusing instead on China's and the region's economy. He pushed for negotiations on a Free Trade Area of Asia Pacific that would include all APEC members, and rejected trade agreements with fewer members. China is not a part of the 12-nation Trans-Pacific Partnership agreement that's led by the U.S. and was signed last month. Obama and the leaders of those economies were scheduled to have their first meeting later on Wednesday on the sidelines of APEC events.

"With various new regional free trade arrangements cropping up, there have been worries about that potential of fragmentation," Xi said.

APEC events continue through Thursday. On Friday, Obama flies to Kuala Lumpur, Malaysia, for the Association of Southeast Asian Nations and East Asia summits.