Amid the steady restoration of its frayed ties Washington, Manila has made a surprise call for a review of the bilateral 1951 Mutual Defense Treaty, the foundation stone of the Philippines' security.

At first sight, the shock announcement that Philippine Defense Secretary Delfin Lorenzana made in late December, seems very odd. Not only does the Philippines face its biggest potential threat of the last 70 years in the shape of an expansionist China.

But the move comes from a ministry that has until now been staunch in resisting pressure from Beijing-friendly President Rodrigo Duterte to undermine Manila's long-standing military ties with Washington.

The Philippine defense chief, who spent more than a decade as a diplomat in Washington, made clear that scrapping the alliance altogether is definitely an option. The treaty allows for unilateral nullification of the agreement within a year of notice.

But Lorenzana's actions may be more subtle than they seem. He is almost certainly not seeking to break the alliance. But by putting the possibility on the table he has a chance of forcing the pro-China lobby around Duterte out into the open -- and pressing these officials to state clearly what kind of security arrangement they seek and how will this protect the country's vital interests, particularly in the South China Sea. If they balk at the prospect of saying bluntly that they would rather trust China than the U.S., this will undermine their arguments and end up strengthening the traditional ties.

At the same time, such a strategy might squeeze some concessions out of Washington to improve what is now a vague mutual defense accord. Of course, Lorenzana is running risks given the unpredictability of both Duterte and U.S. President Donald Trump. But, he is right to try -- because the current deal with Washington desperately needs a much-needed boost.

Even the pro-U.S. elements in Manila share with the pro-China officials a lingering resentment over America's ambivalence over the exact extent of its commitment to its Southeast Asian ally, particularly in light of the South China Sea disputes.

Lorenzana is right in thinking that an upgrade is required for the alliance to reflect 21st century geopolitical realities, namely China's rise and the need for greater American economic engagement with the region.

In exchange for the greater access to strategic Philippine bases bordering the South China Sea, Washington should make clear whether its willing to assist the Philippines in an event of contingencies in the disputed waters.

Moreover, the two allies should finalize economic agreements, including a free trade deal, to revitalize their relations more broadly.

For decades, Washington has equivocated over the parameters of its treaty commitments to the Philippines. As the South China Sea disputes have escalated, pitting the Philippines against other claimant states, the issue has gained greater urgency.

Manila's anxieties go back to two occasions, namely the Mischief Reef (1995) and Scarborough Shoal (2012) crises, when China muscled out the Philippines without any response from Washington from two features within the Philippines' exclusive economic zone.

In both cases, the U.S. professed neutrality and called on the parties to resolve the disputes in accordance with international law.

Manila's anxieties go back to the 1995 crisis over Mischief Reef. (Pictured in May 2016, DigitalGlobe/Getty Images) 

These concerns about the U.S.'s commitment have multiplied since Duterte and Trump took power, with the Philippines leader improving bilateral relations with China while the U.S. president has, repeatedly raised doubts on America's ties with allies.

There are two problems with the Mutual Defense Treaty. First, it does not guarantee automatic American assistance in an emergency.

According to the treaty, each party "would act to meet the common dangers [in their area of jurisdiction] in accordance with its constitutional processes." So, the U.S. Congress, for instance, would have a say on whether the U.S. should assist the Philippines in a conflict.

The second major problem is the exact scope of American commitments. According to the treaty, mutual defense applies in the event of "an armed attack on the metropolitan territory of either of the Parties, or on the island territories under its jurisdiction in the Pacific or on its armed forces, public vessels or aircraft in the Pacific."

Since the 1970s, however, Americans have equivocated over whether Philippine-occupied and -claimed territories in the South China Sea are covered. During his 2014 visit to the Philippines, former U.S. President Barack Obama refused to clarify whether the Treaty would apply in an event of conflict between Manila and Beijing in the South China Sea. He dismissively described the disputed Scarborough Shoal and other Philippine-claimed territories as a "bunch of rocks."

In contrast, the Obama administration made clear the Senkaku/Diaoyu islands, disputed by Tokyo and Beijing, are covered by the 1951 U.S.-Japan Security Treaty, which says that U.S. forces stationed in Japan, "may be utilized to contribute to the maintenance of international peace and security in the Far East and to the security of Japan against armed attack from without."

No wonder then, Lorenzana cited the "ambivalent" attitude of Americans as a pretext for a treaty review. He has also said there were questions on whether the Treaty was "still relevant to our security?" rather than solely "the interest of other nations."

However, a review of the MDT should not serve as an exit strategy but an opportunity to upgrade the alliance, whereby Washington would clarify that its commitments cover currently Philippine-occupied land features in the South China Sea.

In exchange for greater American assurances, the Philippines should consider granting access to bases near the disputed area, namely the Basa and Bautista air bases, and allow American warships to utilize Philippine ports during the Freedom of Navigation Operations tours, which are crucial to maintaining access in important waterways.

Washington's newly-passed Asia Reassurance Initiative Act (ARIA), which allocates an additional $1.5 billion for American security cooperation initiatives in the region, can go a long way in boosting bilateral cooperation.

But upgrading the alliance should go beyond security cooperation and extend to the proposed U.S.-Philippine Trade and Investment Framework Agreement as well as greater American investments in Philippine infrastructure under the recently-passed $60-billion Better Utilization of Investments Leading to Development (BUILD) initiative.

None of these amendments, however, should prevent the Philippines from maintaining stable relations with China, which has offered large-scale commercial deals. Instead, they would place the Philippines in a stronger position to protect its interests in dealings with the Asian juggernaut.

Far from undermining the century-old alliance, the review of the MDT can serve as a springboard to upgrade Philippine-U.S. partnership for the 21st century. This should be Lorenzana's priority. And Duterte's.

Richard Heydarian is a Manila-based academic, columnist and author; his latest book is "The Rise of Duterte: A Populist Revolt Against Elite Democracy."