Reacting to China’s regional assertiveness, U.S. and Filipino forces began joint naval patrols in the South China Sea in March and will now commence air operations, U.S. Defense Secretary Ashton Carter said in a Manila visit on Thursday.

Meanwhile, a nuclear-armed North Korea has entered a “new phase of provocation,” reflecting technological advancement in its weapons program and an increased willingness to use it as leverage, the South Korean ambassador to the U.S., Ahn Ho-young, told an editorial writer last week during a visit to Minneapolis.

The U.S., which has deep defense and diplomatic ties with many Pacific nations, is increasingly being looked at to lead during this destabilization, making President Obama’s Asian “pivot” policy strategically critical. Responding to a rising China is the most important foreign policy challenge for Obama and his successor, whose diplomatic and military approach would benefit by deepening regional economic ties through passage of the 12-nation Trans-Pacific Partnership (TPP) free-trade agreement.

That’s not just the president’s perspective, but the consensus among national security leaders, including 17 former secretaries of defense and retired military leaders who in an open letter to congressional leaders last year wrote: “The stakes are clear. There are tremendous strategic benefits to TPP and T-TIP [the proposed Transatlantic Trade and Investment Partnership], and there would be harmful strategic consequences if we fail to secure these agreements. In both Asia-Pacific and the Atlantic, our allies and partners would question our commitments, doubt our resolve and inevitably look to other partners. America’s prestige, influence and leadership are on the line.”

Secretary of State John Kerry concurred in a Tuesday speech. “Foreign policy is economic policy, and economic policy is foreign policy,” he said. “Without a doubt, these trade agreements are at the center of defending our strategic interests, deepening our diplomatic relationships, strengthening our national security and reinforcing our leadership across the globe.”

Kerry added that “in our era, economic and security interests almost always overlap. And understanding that other nations look to America first for leadership, we know that with TPP, we’re going to be far better positioned to protect our interests in the globe’s most dynamic region with it than we would be without it. … The strategic case for TPP is crystal clear.” Kerry also alluded to China preparing its own version of TPP. But it “wouldn’t raise labor or climate standards or protect intellectual property or promote fair play or, needless to say, insist on a free and open Internet.” And, in fact, allowing China to set trade rules might also embolden its territorial ambitions.

Both Bernie Sanders and Donald Trump have emphasized their opposition to free-trade agreements in stump speeches, and Hillary Clinton now opposes TPP despite touting it when she was secretary of state. It’s unfortunate that the three presidential candidates don’t recognize that beyond the economic benefits of TPP, the agreement would help whoever follows Obama as commander in chief.