If the United States wants a free and open Indo-Pacific, as Secretary of State Rex Tillerson has urged and U.S. President Donald Trump and Japanese Prime Minister Shinzo Abe discussed at their recent meeting in Tokyo, no two powers will be as important as India and Japan.

The two countries are among the most concerned countries aboutthe securityin theregion and are also increasingly ready to work with each other on it. The relationship between the two countries— historically strategically distant—has grown increasingly robust under the stewardship of

Indian Prime Minister Narendra Modi and Abe, with regular high-level summitry Abe traveled to Delhi to visit Modi last month combined with increasingly frequent and deepening exchanges at the diplomatic, defense, and business levels.

One reason, the two countries are coming together is a common strategic anxiety about China’s rise,  particularly its foreign policy ambitions in Asia. For them, Beijing’s maritime assertiveness in the East and South China Seas, as well as the Indian Ocean region, and its push to expand its geopolitical influence beyond East Asia through its Belt and Road Initiative (BRI) and Asian Infrastructure Investment Bank (AIIB) are particularly alarming. India and Japan, in response, have come to share a sense of purpose in promoting the current order in the region, which is based on transparent institutions, good governance, and international law which benefits them by ensuring secure supply chains and fair access to resources.

In addition to the two countries’ shared concerns about the rise of China, there is also anxiety that U.S. credibility is weakening. Despite the efforts of the Barack Obama’s administration’s “rebalance” to the Asia-Pacific,

Washington has been unable to mitigate regional concerns that its influence is diminishing. Such sentiment existed before Trump’s election as President, but it has been magnified by the Trump White House’s America First foreign policy that relies on protectionism and transactionalism rather than a more comprehensive approach to the region. The withdrawal from the Trans-Pacific Partnership (TPP)—which has recently been largely agreed to, in principle by the 11 remaining states in the deal—has further fueled uncertainty among U.S. partners and allies.

Although the United States remains engaged in the region, through a host of bilateral and trilateral frameworks, Delhi and Tokyo see the importance of building complementary diplomatic relationships that largely align with Washington but are not led by the United States. The two have created the Japan-India-Australia trilateral dialogue, which exists independently from frameworks inclusive of the United States. This mechanism, which works at the bureaucratic level, allows Canberra, Delhi, and Tokyo to look at shared perspectives on regional security and synergies on issues such as capacity building and cooperation on humanitarian assistance and disaster relief. And in September, both sides agreed in a joint statement to align their two regional strategies: Japan’s Free and Open Indo-Pacific Strategy and India’s Act East Policy.

Tokyo’s approach focuses on aligning its evolving security and defense posture, which it dubs proactive contribution to peace, with a more expansive vision of the region’s key supply chains, stretching from East Africa to Hawaii. Japan’s embrace of the “convergence of two seas”—as first outlined by Abe more than a decade ago—complements India’s regional approach, called Act East. This policy is an evolution of sorts from India’s former policy of Look East and aims to enhance India’s strategy in East Asia through stronger links to countries in the Association of Southeast Asian Nations especially Myanmar, Singapore, Vietnam, and of course Japan. China’s rapid rise and growing might in the area has created concern in Delhi and prompted the need for a stronger regional approach.

On the security and defense side, there has likewise been much momentum. Japan’s Self-Defense Forces continue to increase cooperation with the Indian military, especially on maritime security issues. Tokyo and Delhi have inked deals on the sharing of military information and the exchange of defense technology. There has also been progress on finalizing India’s long-delayed plans to purchase Japan’s US-2 amphibious plane, a move that

would be a building block for more defense cooperation in the coming years but has been held up for years due to India’s desire to drive down the price per unit as well as questions on the advisability of transferring defense technology. It appears that this deal may soon come through—as indicated by increasing optimism on the issue in successive Abe-Modi summits—and would represent a key next step in the strategic relationship between India and Japan.

In some ways, Japan and India’s friendship is strengthening their ties with the United States as well. In 2016, Delhi and Washington concluded a long-anticipated Logistics of Exchange Memorandum Agreement, which allows each country to use the others’ facilities for refueling, repairs, and other logistical matters. Meanwhile, Tokyo has been dovetailing its efforts to improve defense with Delhi with enhancements in the U.S.-India relationship. And a few months ago, Japan’s Maritime Self-Defense Forces operated alongside the U.S. and Indian navies in the annual Malabar naval exercises. After participating as an ad hoc member for several years, Japan became a permanent member of the exercises in 2015. This year’s Malabar exercise in the Bay of Bengal brought together more than 20 ships, including Japan’s largest naval vessel, the JS Izumo, and nearly 100 aircraft from the three countries. Indeed, Malabar has been a catalyst for growing security cooperation between the United States, India, and Japan and has been complemented by a series of high-level diplomatic engagements, including a meeting of their foreign ministers in September in New York on the sidelines of the U.N. General Assembly.

In turn, trilateral security cooperation has led to growing convergence between Washington and Delhi on security matters, including on Afghanistan and maritime security. In September, U.S. Secretary of Defense James Mattis visited Delhi and stressed the importance of trilateral partnerships in the region,with Japan being the mostimportant.

Indeed, despite its longstanding attachment to nonalignment, India has been increasingly emboldened under Modi to take a more forceful role in the Indo-Pacific. On the diplomatic side, Delhi has been unapologetic about its reservations about China’s BRI and refused to send any representatives

to Beijing’s large inaugural BRI forum earlier this year. On the security side, Delhi has ramped up ties with the United States and Japan and also refused to back down militarily during a tense dispute with China this past September over disputed territory in neighboring Bhutan. Moreover, Delhi unambiguously signaled its concerns with Beijing’s increasing maritime assertiveness by agreeing this week to resume quadrilateral discussions with the Australia, Japan, and the United States—a move Beijing is sure to see as provocative—after a ten-year pause.

There is still plenty of room for even greater cooperation between Delhi and Tokyo, particularly while both remain wary of China. Delhi sees Tokyo as a natural partner, with growing defense capabilities that has developed and nurtured a number of key relationships in the region. And Tokyo sees Delhi as a crucial geopolitical balancer that, despite some difference in strategic thinking, is increasingly willing to step up and contribute to regional security beyond its intractable conflict with Pakistan.

Although India and Japan share common concerns, there is less clarity on how their strategies will converge in practice. From a maritime security perspective, Japan understandably remains predominantly concerned with open sea-lanes and checking China’s assertive behavior in the East and South China Seas. India, meanwhile, remains focused on the Indian Ocean region, where China has expanded infrastructure and investment in Bangladesh, the Maldives, Pakistan, and Sri Lanka.

But these differing regional priorities need not be a point of contention. Indeed, both sides should recognize that their interests in the expansive Indo-Pacific are complementary—that they cooperate on many issues related to maritime security without duplicating efforts. For example, both sides should routinely share their operational capabilities, for example, in defense and coast guard equipment and through training and strategies for building capacity in South and Southeast Asia. Such sharing could be formalized with other like-minded partners, especially the United States and Australia, and housed within the reemerging quadrilateral consultations.

Japan and India must also finalize negotiations on Delhi’s procurement of the US-2 planes. This purchase would be a major milestone in improving their defense, industrial, and acquisition partnership while providing India with the ability to patrol its vast maritime territory, including the Andaman

and Nicobar Islands. Finally, Tokyo and Delhi should work on expanding the scope of their cooperation beyond maritime issues by expanding exchanges and dialogues on such issues as counterterrorism, cybersecurity, and the protection of critical infrastructure.

Robust cooperation between India and Japan has the potential to promote transparency, open sea lines, and adherence to international law in the region. But if they fail, states there will inevitably retrench to their narrower national interests and smaller regional blocs—a scenario that will favor Beijing’s approach to erode mini-lateral groupings it sees as antithetical to its interests.