Mr. Mattis defended the decision to put a spotlight on Iran’s behavior, saying that it was important to make Iran recognize that “it is getting the attention of a lot of people.”
But Mr. Mattis said that the United States did not need to deploy additional military resources to signal its concern. “Right now, I do not think that is necessary,” he said.
Mr. Mattis also signaled restraint on another hot spot: the South China Sea. Mr. Mattis said that China’s territorial claim to almost all of its waters “has shredded the trust of nations in the region.” But he emphasized that he saw no need for more military maneuvers in the area.
“What we have to do is exhaust all diplomatic efforts to try to resolve this properly,” he said.
In a meeting on Saturday morning with Japan’s defense minister, Tomomi Inada, Mr. Mattis reiterated the United States’ commitment to defend Japan in any confrontation with China over disputed islands in the East China Sea, known in Japan as the Senkaku and in China as the Diaoyu.
For the Japanese government, that reassurance was perhaps the most important message of Mr. Mattis’s visit, aside from his confirmation of the United States’ broader commitment to the security of its allies in Asia. During last year’s presidential campaign, Mr. Trump suggested he might pull back from those commitments unless countries like Japan contributed more to the cost of their defense.
On Friday, after Mr. Mattis wound up a two-day visit to South Korea — where he sought to reassure officials that the U.S. commitment to that country’s defense against North Korea had not changed — the defense secretary told Prime Minister Shinzo Abe of Japan that the United States would stand by the countries’ mutual defense treaty.
“I want there to be no misunderstanding during the transition in Washington that we stand firmly, 100 percent, shoulder to shoulder with you and the Japanese people,” Mr. Mattis said at the start of a meeting with Mr. Abe.
During his meeting Saturday with Ms. Inada, Mr. Mattis did not bring up the matter of Japan’s financial commitment to its military defense, according to briefings from both countries.
But in response to a question from a reporter at the Ministry of Defense on Saturday, Mr. Mattis described Japan as “a model of cost sharing and burden sharing” and praised the Abe administration for spending more on the military. Under Mr. Abe, Japan has increased its annual defense budget five years in a row.
Still, the foreign policy community in Japan has begun discussing further increases in military spending, which currently stands at about 1 percent of the country’s economy. “It would not be such a bad thing for Japan to become more self-reliant in terms of security,” wrote the authors of a report from the Institute for International Policy Studies released in Tokyo this week.
The American security presence in Japan is most visibly represented by its military bases across the country, with the largest number of troops concentrated in Okinawa, a chain of islands south of the Japanese mainland.
In his meeting with Ms. Inada, Mr. Mattis confirmed that the United States would proceed with relocating one of its bases, the Futenma Air Base in the south of Okinawa’s main island, to a much less populated area in Nago, also on the main island.
That announcement is likely to anger residents in Okinawa who want the base moved off the island altogether and have long complained about noise and violence. This week, the governor of Okinawa, Takeshi Onaga, visited several members of Congress in Washington to lobby them to persuade the Trump administration to withdraw the base from Okinawa.
On Saturday, Mr. Onaga blasted Mr. Mattis for sticking to the relocation plan, calling it “regrettable.”
As a result, Mr. Onaga said in remarks to reporters in Washington, objections from Okinawans “could be intensified and eventually turned into a protest against the entire U.S. forces, and it could impact the stability of base operations. This could cause serious problems for the U.S.-Japan alliance.”