Seldom do visits by defense officials create so much strategic anticipation as did new US Defense Secretary James Mattis’ just concluded visit to East Asia. America’s erstwhile regional allies are all trying to decipher the difference between US President Donald Trump’s unorthodox rhetoric and communication style, and his administration’s actual policy positions towards the region.

Mattis’ visit was at its core an exercise in strategic reassurance after Trump had raised questions on the campaign trail about his commitment to the future defense of key Asian allies, including Japan and South Korea, where America maintains troops.

In Tokyo and Seoul, Mattis reaffirmed America’s obligations, signaling at least from the outset of Trump’s term that the US’ position had not changed, including in regard to upholding mutual defense treaties and vis-à-vis an increasingly assertive China and saber-rattling nuclear North Korea.

In Tokyo, Mattis told Prime Minister Shinzo Abe that the US would continue to stand “shoulder to shoulder” with Japan and that its commitment to the country’s security remained “ironclad.” The US maintains over 50,000 soldiers in Japan and Mattis made a point of noting he had served personally on the Japanese island of Okinawa.

In Seoul, Mattis told South Korean Defense Minister Han Min-koo that any North Korean nuclear provocation would be met by an “effective and overwhelming” US response. Mattis also said that the US would move ahead with the deployment in South Korea of the Terminal High Altitude Area Defense (THAAD) missile shield system.

Mattis’ stated commitment in a meeting with security officials to defend Japan’s claim to the Senkaku islands, rocky outposts China also claims and refers to as Diaoyu, elicited a strong response from Beijing over the weekend.

Chinese foreign ministry spokesman Lu Kang accused Mattis of jeopardizing regional stability, saying in a statement, “We urge the US to take a responsible attitude, stop making wrong remarks on the issue involving the Diaoyu islands’ sovereignty, and avoid making the issue more complicated and bringing instability to the regional situation.”

Despite Mattis’ tough talk and best diplomatic efforts, there are still deep concerns among America’s Asian allies about the competence and intention of Trump’s wider foreign policy team, according to top level officials who spoke on condition of anonymity.

America’s allies, they say, seek consistency, comprehensiveness and certainty in US strategic engagement in the region, all of which are now in question in light of Trump’s erratic messaging and unorthodox diplomacy. It is thus not clear how much Mattis’ reassurances will have calmed jitters about possible American abandonment or an inadequate US response in a potential conflict situation.

Two weeks into Trump’s tenure, Asian allies have already begun to realize that the US’ highest office – and its rituals of power and self-restraint – have not changed America’s mercurial new leader. If anything, they say, it is Trump that is quickly reshaping the office.

Rather than disowning his controversial campaign promises, Trump has doubled down on his promises to scale back immigration, roll back free-trade agreements and adopt a more transactional approach to diplomacy.

Trump has not only branded China, the world’s largest trading nation, but also named Japan, a key US economic ally, as a currency manipulator. Since taking office, he has reiterated earlier threats to impose a whopping 35% tariff on goods from nations that are deemed to be using anti-competitive means to gain an economic edge.

Economic disengagement from Asia, seen by some in Trump’s fast decision to nix the Trans-Pacific Partnership (TPP) trade pact, will inevitably strengthen China’s hand and shake a key pillar of America’s strategic relationships, the officials say.

Over the past decade, Beijing has become the leading trade partner of almost all of Asia, and is moving ahead with consolidating its economic influence via finalization of alternative free-trade agreements, namely the Regional Comprehensive Economic Partnership (RCEP) and Free Trade Area for the Asia-Pacific agreement (FTAAP). China has suddenly and vocally emerged as the new vanguard of the global free-trade order and main engine of future Asian growth.

Key American allies such as Australia and New Zealand, keen to tap that growth potential, have already proposed a “TPP-minus-one” (meaning America) initiative, with Canberra going as far as to invite China to join the previously US-led multilateral trade pact from which it was earlier strategically excluded. As a senior official from a key US ally in Asia said in a recent closed-door multilateral discussion in Canberra, “This is perhaps how superpowers commit suicide.”

Still, Mattis’ security related messages were cause for cautious optimism among its strategic allies. Trump, his key strategic advisor Steve Bannon, and new Secretary of State Rex Tillerson have all intimated the US will take a more muscular approach to China’s rising assertiveness, including in the contested waters of the South China Sea.

As one former Australian rear admiral told this writer, “Now the Chinese are beginning to take America seriously again, proceeding with greater caution than before.”

Senior Japanese officials expressed similar sentiments about the new US administration’s defense posture. In particular, Japanese officials believe that Trump will not hesitate to directly challenge China’s expanding military and para-military footprint in the South China Sea.

Mattis reassured regional allies on every stop of his Asian tour that the Trump administration will continue, and even bolster, the outgoing Barack Obama administration’s strategic “pivot” to Asia.

In that direction, Mattis accused Beijing of “shredding the trust” of regional states and encouraged China to “play by the rules,” a not-so-veiled reference to the United Nations Convention on the Law of the Sea (UNCLOS).

He also called on China to refrain from “taking military means and occupying land that is subject to question, to say the least, about who actually owns it,” in referring to the South China Sea disputes. While certain allied officials applauded Mattis’ firm recommitment to the region’s security, others fretted Trump’s tough talk could tilt an already volatile region towards armed conflict.

Indeed, the apparent strong influence of hawkish ideologues in Trump’s policy team has raised concerns among some allies that advocates of continuity and a measured American posture could be drowned out by more hard-line voices, including National Security Council member Bannon, who before Trump’s election explored in his journalism the idea of sparking conflict with China to nip its ascendency in the bud.

If the latter camp outpaces the former, the officials say, Trump’s Asian policy will be strong on threats, void on economic engagement and lacking in diplomatic calibration.