The two refurbished American navy vessels that joined the Philippine fleet on Monday will bring "real" and "strategic" benefits not only to the country, but also to its alliance with Washington and to the region, US Ambassador to the Philippines MaryKay Carlson said.

During the Christening and Commissioning of BRP Valentin Diaz and BRP Ladislao Diwa, both Alvarez-class patrol vessels, Carlson said the vessels were entering into service "at an important time when the maritime security environment in the Indo-Pacific is increasingly complex."

Amid China's aggression in the South China Sea, the Philippines and the US have committed to uphold rules-based order and deter actions that will undermine peace and stability in the region.

Carlson said the mission that the vessels will undertake "will not be easy" as they will patrol the Philippine waters, protect the legitimate economic activities, fight against illegal fishing as well as deliver human assistance and disaster relief.

"I commend the brave sailors who serve aboard them. Their dedicated service and the missions they undertake are central to the shared US-Philippine goal of ensuring a free, open, and prosperous Indo- Pacific region," Carlson said.

According to Carlson, the transfer of the ships from the US Navy to its Philippine counterpart "has much more than symbolic value."

She said it symbolized America's continued support for the Philippine Navy, which is on the frontline of defending the country's sovereign rights in the South China Sea, particularly over the West Philippine Sea.

"This commissioning is also the latest illustration of our continued collaboration in pursuit of the modernization goals of the Armed Forces of the Philippines. The Philippines is the largest recipient of US military assistance in the Indo-Pacific, merited by the ambitious agenda we have set together for our alliance," Carlson said.

Valentin Diaz and Ladislao Diwa have been commissioned to join the Philippine Navy's fleet through US military financing worth P780 million (13.8 million USD).

"As the Philippines continues its courageous stand to uphold the international order and defend its rights in the West Philippine Sea, rest assured the United States stands with you in this all-important endeavor," Carlson said.

Previously named USS Monsoon and USS Chinook, Valentin Diaz and Ladislao Diwa used to patrol the waters of the Arabian Gulf in support of operations in the Middle East, including Operations Enduring Freedom and Iraqi Freedom.

"These two vessels have a significant history of service at the forefront of operations for the United States Navy," Carlon said. "After refurbishment through U.S. funding, they are now ready to join the Philippine Navy Littoral Combat Fleet."

The US envoy said Manila and Washington have now "come together to reflect on the ways in which the BRP Valentin Diaz and BRP Ladislao Diwa will protect and defend the Philippines and strengthen our alliance."

"And that is something very much worth celebrating," she added.