Amid speculation about how the Obama administration has responded to Japanese Prime Minister Shinzo Abe's visit to a highly controversial war shrine, the State Department reiterated Washington's explicit disappointment Thursday.

"The United States is disappointed that Japan's leadership has taken an action that will exacerbate tensions with Japan's neighbors," Jen Psaki, the department's spokeswoman, said in an emailed statement.

Her four-paragraph statement contained exactly the same wording as that issued by the U.S. Embassy in Tokyo earlier.

The department has skipped its daily press briefings throughout this week as announced before, apparently attributable to the Christmas holiday.

Abe became Japan's first prime minister to pay homage at the Yasukuni Shrine in Tokyo in seven years. The shrine honors 2.5 million war dead, including 14 people convicted as criminals by a 1948 war tribunal.

South Korea, China and some other nations view the shrine as a major symbol of Japan's militaristic past.

Diplomatic sources here said U.S. officials are apparently shocked and irked by Abe's move.

The U.S. government's message has become much tougher than the response to the previous Yasukuni visit in 2006 by then-Prime Minister Junichiro Koizumi. In diplomacy, the use of the word "disappoint" toward an ally is unusual.

"These are going to be decisions that Japanese politicians and Japanese prime ministers are going to have to make for themselves,"

State Department spokesman Sean McCormack said in a news briefing at that time.

Some observers, however, take issue with the format of Washington's first statement this time, which came from the embassy in the Japanese capital.

In an email to Yonhap News Agency, Caitlin Hayden, spokeswoman for the White House National Security Council, just said that, "We would refer you to the statement released by the U.S. Embassy in Tokyo."

Another U.S. official advised Korean media "not to read much" into it.

The embassy released the first statement just because of a time difference between Washington and Tokyo, the official told Yonhap on background.

Meanwhile, an informed source said Abe's shrine visit poses a greater challenge to Seoul's two-track approach on its relations with Tokyo -- making no concession on history issues but taking a forward-looking attitude in dealing with other affairs.

Regarding Abe's remarks during the visit, the U.S. government said in the statement, "We take note of the Prime Minister's expression of remorse for the past and his reaffirmation of Japan's commitment to peace."

The source said the U.S. message appears to reflect its hope that Abe will carry out his stated commitment. (Yonhap News)