Washington- Henry A. Kissinger slipped into the State Department last week for a quiet lunch in his old office with Rex W. Tillerson, the former Exxon Mobil chief executive, who has all but covered himself in a cloak of invisibility in his first six weeks as secretary of state.

Describing his impressions, Mr. Kissinger, perhaps America’s most famous diplomatic strategist, chose his words judiciously. “The normal tendency when you come into that job is to increase your visibility and to show that you are present and in charge,” he said in an interview. “He wanted to first inform himself of all the nuances. I was impressed by the confidence and self-assurance that he showed.”

But in the Washington of Donald J. Trump, where foreign policy proclamations often appear first on Twitter, and where White House advisers are still battling for dominance, this approach can be seen as brilliant, mystifying or a prescription for powerlessness.

Mr. Tillerson has skipped every opportunity to define his views or give guidance to American diplomats abroad, limiting himself to terse, scripted statements, taking no questions from reporters and offering no public protest when the White House proposed cutting the State Department budget by 37 percent without first consulting him.

He suffered in silence, State Department officials said, when President Trump called, in a matter-of-fact way, to reject Mr. Tillerson’s choice for deputy secretary of state. He has been absent from the White House meetings with key world leaders, and when the State Department issued its annual report on human rights — usually a major moment for the United States to stand up against repression around the world — he skipped the announcement.

Defenders say Mr. Tillerson has been accomplishing far more behind the scenes.

“He’s already developing plans to begin ratcheting back Putin’s nefarious behavior,” Senator Bob Corker, the chairman of the Senate Foreign Relations Committee, said in an interview — steps that would represent the first known effort by the new administration to face off against President Vladimir V. Putin of Russia.

“He’s won status and respect of the president, of McMaster, and talks all the time to Jared,” the senator said, referring to the national security adviser, Lt. Gen. H. R. McMaster, and Jared Kushner, Mr. Trump’s son-in-law, who has emerged as a prominent voice on American foreign policy.

“He doesn’t mind at all that these stories are being written about him being missing,” Mr. Corker, a Tennessee Republican, said about Mr. Tillerson. “When he’s ready to talk, you will be very highly impressed.”

On Tuesday, Mr. Tillerson will leave for his first truly fraught diplomatic mission: a trip to Japan, South Korea and China, at a moment when open conflict with North Korea is a growing possibility, and when the administration is planning Mr. Trump’s first meeting with President Xi Jinping of China. The trip is so vital that the “principals” committee of the National Security Council is set to convene on Monday to discuss the North Korean threat and how to deal with China, so that Mr. Tillerson speaks from a consensus strategy.

But do not expect to hear much about that strategy from the secretary before he arrives in Asia: The State Department has told reporters that they cannot ride on the plane. The decision appears to be unprecedented for a major diplomatic trip — even four decades ago, when Mr. Kissinger was conducting shuttle diplomacy in the Middle East and opening up China, he was delivering spin to reporters on the plane and offering up diplomatic tutorials.

“All his predecessors have traveled with press,” said R. Nicholas Burns, who served as spokesman, ambassador and under secretary of state in both Republican and Democratic administrations. Failing to do so, he noted, creates the risk that the secretary of state will be defined by the country he is visiting — especially a place like China.

Within the State Department, Mr. Tillerson, 64, got off to a promising start with a warm, humble greeting to staff members in the drab headquarters’ flag-draped foyer on his first day on the job. He talked about his upbringing and his wife’s belief that he had been preparing for this job his whole life, even if had not known it.

But few have heard from him since. Those who have say they regard him as an impressive manager who knows how to run a crisp meeting, take in a variety of views and give little away about his own.

“He forces everyone to boil their memos down to a page or two, so they really have to think about what their message is,” said one official who has dealt with him frequently in recent weeks. “He’s already met with two of the most important Chinese officials. He knows a lot about some countries many secretaries don’t know about,” including Indonesia and others that have energy assets. He understands what embassies do, because Exxon Mobil often relied on them for help.

But he is also introverted, a bit standoffish. He never met in person with John Kerry, his predecessor. “These guys came in to drain the swamp,” one career State Department official said, “and it’s clear that they are under orders not to cooperate or deal with swamp creatures.”

So, for thousands in the State Department, Mr. Tillerson has come to be viewed as the phantom of Foggy Bottom, scarcely glimpsed and known mostly for his directives to wipe out some of the department’s top jobs.

Longtime career officials who expected to stay in their jobs or remain long enough to show their successors the ropes were ousted in Mr. Tillerson’s first two weeks. He is talking to members of Congress about further cuts, and while there are plenty of opportunities in a department that has not exactly embraced technological change, the major reductions proposed by the administration are a nonstarter with many lawmakers.

The biggest concern among diplomats and many in Congress is that when Mr. Trump talks about bolstering America’s commitment to its national security, he does not have diplomacy in mind. Longtime diplomats often cite — or email to reporters — a line uttered four years ago by the new defense secretary, Jim Mattis, when he was in charge of Central Command.

“If you don’t fund the State Department fully, then I need to buy more ammunition,” Mr. Mattis said at the time. As one diplomat who has met frequently with Mr. Tillerson since he took office noted recently, “Rex clearly agrees with that. He just won’t say it.”

(A senior State Department official said Mr. Tillerson did say it, to Mr. Trump, over dinner a little more than a week ago.)

On his first trip, to Europe, Mr. Tillerson went out of his way to reassure allies of the United States’ commitment to NATO, doing little to repeat the “America First” notion that Mr. Trump has promoted. In Asia, Mr. Tillerson is scheduled to visit the Demilitarized Zone on the border with North Korea, and it seems almost unimaginable that he would repeat Mr. Trump’s warning as a candidate that the United States may pull back from the region.
Secretaries of state from both parties have relished their role as chief spokesman for American values.

Madeleine K. Albright made her name describing the United States as the “indispensable nation” that needed to intervene in the Balkans. Colin L. Powell took the lead in making the case for invading Iraq (words he later regretted). Hillary Clinton, under President Barack Obama, highlighted human and women’s rights in particular. Mr. Kerry narrated his own role as relentless negotiator, sometimes using background briefings to read aloud from copious handwritten notes he had taken while haggling over the Iran nuclear deal and the removal of chemical weapons from Syria. In indiscreet moments, he talked about his differences of view, mostly on Syria, with Mr. Obama.

The New York Times