FILE - U.S. and Philippine troops disembark from an assault vehicle during a joint exercise at the Naval Education and Training Command at San Antonio township, Zambales province, northwest of Manila, Philippines, April 21, 2015.
FILE - U.S. and Philippine troops disembark from an assault vehicle during a joint exercise at the Naval Education and Training Command at San Antonio township, Zambales province, northwest of Manila, Philippines, April 21, 2015.

MANILA, PHILIPPINES - A U.S.-Philippine defense agreement that would help counter China's growing naval power in the disputed South China Sea has yet to be implemented more than a year after it was signed, and could now face a fresh political hurdle in Manila.

The deal gives U.S. troops wide access to local military bases and approval to build facilities to store fuel and equipment for maritime security, but it was effectively frozen after left-wing politicians and other opponents challenged its constitutionality in the Philippine Supreme Court last year.

The court is expected to issue a ruling before President Barack Obama visits Manila for an Asia-Pacific summit in November. The deal, called an Enhanced Defense Cooperation Agreement (EDCA), was signed just days before Obama last traveled to Manila in April 2014.

In another complication, 13 senators in the 24-member Philippine Senate have signed a draft resolution insisting the upper house scrutinize the deal before it takes effect.

"In this resolution, we are saying we will not allow the power of the Senate to be eroded," Senator Miriam Santiago, the principal author of the measure, said in a statement last week.

The proposed resolution will be lodged in late July, when the Senate reconvenes after a recess.

Not binding on Aquino

While a Senate resolution would not be binding on President Benigno Aquino, it would put pressure on him to allow senators to debate the agreement, which would delay it further, Philippine political experts told Reuters.

With national elections due in May 2016, politicians are already focusing on who will contest the presidency when Aquino steps down, possibly putting some congressional business on the back burner. The Philippine constitution allows presidents to serve only a single, six-year term.

"Aquino is increasingly losing his power to influence Congress," said political expert Ramon Casiple.

Further delays might raise eyebrows in Washington, experts said, given Manila has been the most vocal critic of Beijing among the claimants to the South China Sea and has urged the United States to be more assertive in pushing back against China's rapid land reclamation in the waterway.

Senators have said they also want to review an agreement to be negotiated with Tokyo that would allow Japanese military aircraft and naval vessels to use bases in the Philippines for refueling and picking up supplies.

The Senate has ratified previous Philippine defense agreements, including a decades-old security treaty with the United States. Aquino has said the EDCA needs only executive approval because it's an addition to existing security arrangements.

Broader access by U.S.

To be sure, U.S.-Philippine military ties are already robust. Philippine military officials say there has been an increase in U.S. exercises, training, and ship and aircraft visits in the past year under Obama's "rebalance" to Asia.

But the EDCA would take the relationship a step further, partly by giving U.S. forces broad access to the Philippines.

Washington, for example, wants to use Philippine military bases in eight locations to rotate troops, aircraft and ships, the Philippine military chief said in April. One of those is a base on Palawan island, about 160 kilometers (100 miles) from the Spratly islands, where China's creation of seven artificial outposts will allow Beijing to project power into the maritime heart of Southeast Asia.

The agreement would also allow the U.S. military to build infrastructure such as barracks, logistic warehouses and fuel depots for its visiting forces.

U.S. Marine Lieutenant Colonel Jeffrey Pool, a Pentagon spokesman, acknowledged that the court process had delayed implementation.

"There have been informal, working-level discussions of potential locations and next steps, but no final decisions have been made, nor are there any plans to begin implementing the EDCA until the Supreme Court completes its review," said Pool.

Signal of uncertainty?

A Senate resolution on the EDCA would not go unnoticed at the court, the Philippine political experts added. While the court is independent, it would be taking note of the political winds while also paying attention to concerns over China's muscle flexing in the South China Sea, they said. Even if the court ruled the agreement was constitutional, it might say it needed Senate approval, they said.

Theodore Te, the Supreme Court spokesman, said the resolution would not influence the court's decision, although he noted that the issue of a Senate review of the defense deal had been raised during oral arguments in court.

Any delays in the court decision could send a signal to Beijing that Manila was uncertain about its alliance with the United States, said Ernest Bower, a Southeast Asia expert at the Center for Strategic and International Studies in Washington.

"If the Supreme Court does not move expeditiously on the EDCA and the agreement is not in place before Obama's visit, the White House will have to ask whether the Philippines is serious about implementing its treaty alliance with the United States," Bower wrote recently.