The Philippine Supreme Court ruled Tuesday a military accord with the United States was constitutional, paving the way for a greater presence of US forces in the former American colony as tensions simmer in the South China Sea.
The 10-year agreement, signed in 2014 but not implemented due to legal challenges, will see more US troops rotate through the Philippines for war games and help their hosts build military facilities.
Supreme Court spokesman Theodore Te said the accord was upheld with a 10-4 vote, ruling that President Benigno Aquino's government had the authority to sign the pact and did not need congressional approval.
The pact "is a mere implementation of existing laws and treaties," Te said.
Aquino negotiated the accord to help the Southeast Asian nation improve its military capabilities and draw the United States closer, partly in a bid to counter a fast-expanding Chinese presence in disputed parts of the South China Sea close to the Philippines.
US President Barack Obama also pushed hard for the Enhanced Defense Co-operation Pact (EDCA) as part of his so-called strategic "pivot" to Asia that has involved expanding American military presence in the region.
However it faced immediate legal challenges from groups opposed to US military involvement in the Philippines, a US colony from 1898 to 1946.
The Philippines hosted two of the largest overseas US military bases until 1992, following a Filipino Senate vote to end their leases that was influenced by anti-US sentiment.
The EDCA agreement was signed in April 2014 as Obama visited Manila, when he said it would give US forces "greater access to Filipino facilities, airfields and ports, which would remain under the control of the Philippines".
Filipino officials also previously said it would allow the United States to store equipment that could be used to mobilise American forces faster -- particularly in cases of natural disasters such as the frequent typhoons that batter the archipelago nation.
The Philippines and the United States are already bound by a mutual defence treaty signed in 1951 and a visiting forces agreement signed in 1998.
The first accord commits the United States to come to the aid of the Philippines in case of external aggression, while the second paved the way for US troops to engage in exercises in the Southeast Asian nation.
The new pact, which was only intended to be in place for 10 years from 2014, does not authorise a return of US bases.
The cash-strapped Philippines, which is also battling communist and Muslim separatist insurgencies, has heavily relied on US military aid for weapons and training.
But in recent years the tensions with China have seen Aquino's government seek much greater US military and diplomatic support.
China claims almost all of the South China Sea, despite conflicting claims from the Philippines as well as Vietnam, Malaysia, Taiwan and Brunei.
In April 2012, after a tense stand-off with Philippine ships, Chinese vessels took control of a shoal just 220 kilometres (135 miles) off the main Philippine island of Luzon.
The Philippines has since become the most vocal critic of China's efforts to claim South China Sea territory, including its strategy of turning islets in those waters into artificial islands that can host military facilities.
In a short statement immediately after the Supreme Court's announcement, the US embassy in Manila welcomed the verdict.
"EDCA is a mutually beneficial agreement that will enhance our ability to provide rapid humanitarian assistance and help build capacity for the Armed Forces of the Philippines," the statement said.
U.S. military forces take part in the annual ''Balikatan'' (shoulder-to-shoulder) war games with Filipino soldiers on the shore of San Antonio, Zambales in northern Philippines April 21, 2015. Reuters