TOKYO — North Korean weapons tests this month clearly violated United Nations Security Council resolutions, John R. Bolton, the White House national security adviser, said on Saturday, going further than President Trump in characterizing the tests of short-range ballistic missiles.
Mr. Trump initially declared he was “not happy” with the tests but then played down their importance.
“In terms of violating Security Council resolutions, there is no doubt about that,” Mr. Bolton said, speaking in Tokyo in advance of Mr. Trump’s four-day visit to Japan. “I think the prime minister and president are going to talk about making sure the integrity of the Security Council resolutions are maintained,” he said, referring to a Monday summit meeting between Prime Minister Shinzo Abe and Mr. Trump.
Mr. Bolton said that the United States fully supports efforts by Japan’s prime minister to meet with Kim Jong-un of North Korea without any preconditions.
Mr. Bolton said the president had already had “two unconditional meetings with Kim Jong-un,” in Singapore and Hanoi, and he did not see “anything untoward” in Mr. Abe pursuing a similar meeting with the North Korean leader.
Until recently, Mr. Abe had said that he would only meet with Mr. Kim after the North Korean dictator had taken concrete steps toward denuclearization and agreed to resolve a dispute over Japanese citizens abducted by North Korea in the 1970s and ’80s.
But in a retreat from that hawkish position this month, Mr. Abe said he would be willing to meet Mr. Kim on an “unconditional” basis.
Mr. Bolton said that such a meeting could help further the effort to denuclearize North Korea as well as resolve the issue of Japan’s abductees, a top priority for Mr. Abe that he had mentioned in virtually every meeting or phone call with Mr. Trump.
“Given Abe’s willingness to hold this meeting with Kim Jong-un,” Mr. Bolton said during a briefing with reporters, “it would certainly be in North Korea’s interest to accommodate the prime minister.”
The national security adviser said the United States had not heard much from North Korea since the summit meeting in Hanoi in February, which ended abruptly after Mr. Trump rejected Mr. Kim’s suggestion that Washington lift the most painful of sanctions imposed on his country since 2016 in exchange for a partial dismantlement of its nuclear weapons program.
“We really have not heard much from North Korea since the Hanoi summit,” Mr. Bolton said. He added that United States officials were “ready to have further discussions at the working level to see what progress might be made.”
Mr. Bolton said that Stephen Biegun, Mr. Trump’s special envoy for North Korea, “can’t wait to talk to his North Korean counterpart but they have not responded.”
“He is ready at any point to get on a plane and go anywhere to talk to them,” he added.
North Korea has warned the United States that its seizure of a cargo ship from the North could thwart any future disarmament talks between the two countries. Mr. Bolton said the seizure was an “appropriate action.”
“Maybe now is an appropriate time to talk about the return of the U.S.S. Pueblo,” Mr. Bolton said, referring to the naval intelligence ship that was attacked and captured by North Korea in 1968 and is still held in a river in Pyongyang, the North’s capital.
Mr. Bolton scoffed at a recent statement made by an unnamed Foreign Ministry official in North Korea that the country would not enter further negotiations “unless the United States puts aside the current method of calculation and comes forward with a new method of calculation.”
“Having many years ago been called ‘human scum’ by the North Koreans,” Mr. Bolton said, “I take much of what they say with a grain of salt.”