Earlier this year, Japan’s relationship with the United States seemed to be on solid footing.

Prime Minister Shigeru Ishiba met with President Trump at the White House in February and pledged to significantly boost investment in the United States. The two leaders talked about their “unwavering commitment” to what some U.S. diplomats have called the most important bilateral relationship in the world, bar none.

Those ties appeared to count for something when the Trump administration announced so-called reciprocal tariffs on dozens of trading partners on April 2. Sure, the 24 percent rate handed to Japan from the top buyer of its goods was a blow. But Japan was the first major trade partner invited to Washington to negotiate those tariffs away.

Now, Japan is dealing with diplomatic whiplash.

On Monday, Mr. Trump delayed until Aug. 1 tariffs that were supposed to take effect on Wednesday for dozens of countries. Japan was among a subset of countries, along with a neighbor, South Korea, that received letters directing them to change what the White House called unfair trade policies.

The announcement that Japan would be targeted with a new 25 percent tariff came after a week in which Mr. Trump repeatedly lashed out at the country, an ally, for its unwillingness to buy American cars and rice. He characterized Japan as “spoiled” and indicated that a trade deal was unlikely.

On Tuesday, Mr. Ishiba said Japanese government officials had engaged in “earnest and sincere discussions” with counterparts in the United States. Mr. Ishiba called the U.S. announcement “deeply regrettable.”