A diplomatic tightrope

There is no dearth of highly sensitive topics for Tillerson to discuss with his counterparts in Japan, South Korea and China - the three nations he is visiting from March 15-19. This is Tillerson's first visit to the region as the US' chief diplomat.

It comes during challenging times when tensions are running high in Northeast Asia. US allies in the region - Japan and South Korea - are perturbed and worried about their reclusive and bellicose neighbor, North Korea.

Pyongyang's nuclear and missile tests have increased in frequency and sophistication over the past couple of years.

The North carried out two nuclear tests and launched some 20 ballistic missiles in 2016 alone. Earlier this month, Pyongyang fired multiple missiles which flew about a thousand kilometers into the sea near the coast of Japan.

The North's nuclear and missile development seems to continue unabated despite the international community's repeated warnings and sanctions. Pyongyang's aggressive posture has unnerved not only Tokyo and Seoul, but also what the world perceives as the isolated regime's sole ally, China.

Tensions over THAAD

In response to the threat posed by the North, Washington a week ago began to install an advanced anti-missile system, called the Terminal High Altitude Area Defense (THAAD), on South Korean soil. The move shows that the new Donald Trump US presidential administration is holding on to the policies of former President Barack Obama in the region.

The United States has also started to deploy "Gray Eagle" attack drones to South Korea, a US military spokesman said on Monday.

American and South Korean troops are also conducting their annual large-scale joint exercises, which they say are defensive in nature, from March 1 until the end of April.

The exercise last year involved about 17,000 American troops and more than 300,000 South Koreans. South Korea has said this year's exercise would be of a similar scale.

Despite its misgivings about the North's belligerent outbursts, China has voiced vehement opposition towards the US moves in South Korea. Beijing is irked by the prospect of having to contend with THAAD in South Korea, as it fears the system's powerful radar can gaze deep into Chinese territory and compromise its own defenses.

China has also called on South Korea and the US to stop their exercises, saying that they do nothing to ease soaring tensions on the Korean Peninsula. In exchange, Beijing has asked the North to halt its weapons tests.

Building trust

Against this backdrop, Tillerson's trip will be closely watched for hints at how the new administration in Washington intends to tackle the complex regional security environment.

"It is extremely important that Japan and the United States closely and frequently communicate given the changing security environment in the region," Japanese Foreign Minister Fumio Kishida told reporters in Tokyo on Tuesday. "I hope to have a frank exchange of views on various issues, including on North Korea," he added.

Japan and South Korea will also seek reassurance from Tillerson regarding the US commitment to their defense. Both countries were castigated by Trump during his fiery presidential campaign for freeriding on US security guarantees. The US currently has around 54,000 troops stationed in Japan and about 28,500 in South Korea.

Trump demanded that they pay up for the resulting costs borne by the US and even suggested the two nations should develop their own nuclear weapons. The statements rankled Tokyo and Seoul, undermining their confidence in the US' protection shield.

Trump's rhetoric, however, has veered since becoming president. For instance, when Japanese PM Shinzo Abe visited the US last month, Trump assured him that the alliance would remain strong, saying: "The bond between our two nations and the friendship between our two peoples runs very, very deep."

Still, doubts abound about the unpredictable and capricious president's commitment. Tillerson's trip therefore is a chance for the US administration to soothe frayed nerves and set its future course in Asia on a firmer footing.

A Trump-Xi summit?

The final leg of the US secretary of state's trip takes him to China, a country that is seen by the Trump administration as a geopolitical and economic competitor.

During his campaign, Trump strongly criticized China, accusing Beijing of unfair trade policies and of not doing enough to rein in North Korea, among other issues. The relationship soured further following Trump's unprecedented phone call with Taiwan's president after his election and his calling into question the so-called "one China" policy.

While these statements caused friction between Beijing and Washington, relations appear to have been repaired somewhat following Trump's phone call with Chinese President Xi Jinping. During the conversation, Trump sought better ties and agreed to honor the longstanding "one China" policy.

During his visit to China on Saturday and Sunday, Tillerson will meet Xi and other leaders and seek ways to ameliorate the bilateral relationship further.

The secretary of state is also expected to lay the groundwork for a potential summit between Donald Trump and Xi Jinping in the coming weeks.

"Planning is ongoing for a visit between President Trump and President Xi at a date to be determined," White House Press Secretary Sean Spicer said on Monday.

In previewing Tillerson's Asia visit, US Acting Assistant Secretary of State Susan Thornton told reporters it would "to some extent be paving the way for future high-level meetings between our two presidents," Reuters reported.