Tokyo is worried midrange North Korean projectiles that could target Japan would be left out of agreements the United States and the North could reach next week, the Asahi Shimbun reported Thursday.
The report comes a day after the White House said Trump spoke to Japanese Prime Minister Shinzo Abe by phone to "reaffirm their commitment to achieving the final, fully verified denuclearization" of North Korea.
Critical voices in the Japanese government are on the rise, however, according to the Asahi. Japanese critics say they do not expect North Korea to disclose a list of its nuclear facilities, or agree to a timetable for denuclearization, which have been part of U.S. demands.
Japanese government officials are also worried Trump will be rushed to produce results at the upcoming summit, focusing on North Korea's intercontinental ballistic missiles while neglecting to address other threats from Pyongyang.
Wariness about the United States and Trump's "America First" approach to foreign policy is growing in Japan; a recent Pew research poll shows 66 percent of Japanese surveyed said "U.S. power and influence" is a "rising concern."
Yomiuri Shimbun reported this week Japanese officials have privately voiced concern about a potential "loose compromise" that could be reached at the upcoming summit in Hanoi, even as Tokyo has publicly reaffirmed support for the meeting.
Trump had recently said he is in "no rush" to denuclearize North Korea.
The remarks and other signals mean Trump and Kim could achieve "positive results" in Hanoi, South Korean presidential adviser Moon Chung-in said.
Moon, who was at Duke University to address peninsula issues on Wednesday, also said North Korea could "very soon be willing to dispose of nuclear weapons."
Both leaders could face domestic opposition if results are not achieved, Moon said, according to South Korean paper JoongAng Ilbo.