WASHINGTON >> Secretary of State Rex Tillerson plunges this week into the increasingly volatile situation in North Asia with visits to Japan, South Korea and China, the region’s central players for dealing with North Korea’s missile launches and nuclear tests. Complicating the mission are Chinese concerns about how the U.S. has responded so far.

Beijing strenuously objects to the initial deployment to South Korea of a U.S. missile defense system. One of Tillerson’s chief tasks will be to assuage Asia’s biggest country and arrange a much-anticipated visit by Chinese President Xi Jinping to the United States.

Tillerson’s four-day trip will be closely watched for signs of how the Trump administration will approach the escalating tensions with North Korea, whose leader has disregarded international appeals to disarm and accelerated weapons development. The North conducted two nuclear tests and 24 ballistic missile tests last year, deepening concern in Washington that it could soon develop a nuclear-tipped missile capable of reaching the U.S. mainland.

Last week, North Korea launched four missiles into the ocean off Japan as the U.S. and South Korea began annual drills. The allies call the drills routine. Pyongyang regards them as an invasion rehearsal.

The Trump administration is searching for new ideas to stop North Korea in ways that years of international sanctions and diplomatic isolation have failed to do.

While administration officials say all options are on the table, including military ones, early signs indicate the U.S. wants to ensure current sanctions are properly applied, targeting the government’s revenue sources and ability to import sensitive technology usable in nuclear weapons and missiles.

For now, there appears to be no desire to negotiate with North Korea — a holdover stance from the Obama administration, which demanded the North first commit to the goal of denuclearization. But U.S. officials have been vague about what their new approach might entail.

All eyes are now on Tillerson as he tries to navigate the complex and sometime acrimonious relationships necessary for formulating a regional strategy. It’s a task President Donald Trump complicated last year by challenging Japan and South Korea to contribute more to their own defense and questioning the fundamentals of four decades of U.S. diplomacy with China. But since taking office, Trump has sought to allay those concerns.

Tillerson will travel on a small plane without a contingent of journalists or a designated pool reporter who would send reports to the broader diplomatic press corps, departing from 50 years of practice and even from Tillerson’s earlier official overseas trips to Germany and Mexico.

The State Department says it will accommodate U.S.-based reporters traveling to Asia commercially by providing them access to Tillerson’s public events at each stop. But commercial flights don’t easily align with Tillerson’s schedule, making such coverage more difficult.

Reporters have traveled with the secretary of state to report quickly on developments in foreign negotiations. They also question U.S. diplomats in front of their counterparts. Such practices allow immediate and comprehensive coverage of the diplomacy at hand. Journalists also are present if something untoward happens to the secretary of state. In 2015, John Kerry fell off his bicycle outside Geneva, breaking his leg at a delicate moment in Iran nuclear negotiations.

Some U.S. lawmakers are concerned Tillerson risks letting foreign governments shape coverage and sending a message that Washington isn’t committed to supporting a free press. Sen. Edward Markey, a Massachusetts Democrat, urged Tillerson last week to reconsider. It wasn’t clear if the decision might be amended.

Tillerson arrives Wednesday in Japan and will meet Prime Minister Shinzo Abe the next day. Abe has courted Trump, visiting the president’s Mar-a-Lago resort in Florida last month. North Korea marked the occasion by test-launching a new type of solid-fuel missile.

Tillerson then visits South Korea, caught up in political upheaval after last week’s ouster of its president, Park Geun-hye, over a corruption scandal. Park had been in lockstep with Washington’s efforts to isolate Pyongyang. The favorite to succeed her is Moon Jae-in, a moderate who wants to engage North Korea’s government.

Tillerson’s final leg involves meetings with several senior Chinese officials in Beijing. Relations are delicate after the U.S. and South Korea began the deployment last week of a missile defense system they say targets North Korea. Beijing claims the radar can range inside Chinese territory and weaken its nuclear deterrent.

The dispute threatens Washington’s effort to get Beijing to exert more economic pressure on its traditional ally, North Korea. China recently suspended North Korean coal imports, a major source of revenue for Pyongyang. China now wants the U.S. to restart nuclear talks with the North.