Nearly a month after President Trump became the first sitting U.S. president to walk on North Korean soil, the euphoria from his meeting with Kim Jong Un faded this week as North Korea fired off two short-range ballistic missiles, unveiled a high-tech submarine and rejected foreign food aid for millions of its impoverished citizens.

The primary accomplishment of Trump’s June 30 visit to the Korean border was an agreement to relaunch working-level talks in “two or three weeks,” Secretary of State Mike Pompeo said at the time. But that time frame has come and gone, raising the question of whether Pyongyang’s truculent behavior represents an about-face on its commitment to hold talks or is simply a negotiating tactic ahead of the meetings.

For Trump, North Korea’s brinkmanship threatens to complicate his reelection message that his diplomacy has dramatically reduced the likelihood of war on the Korean Peninsula and set the stage for a historic denuclearization deal.

State Department officials had hoped to begin the talks, led by special envoy Steve Biegun, as early as next week, but North Korea’s missile launches are likely to delay those meetings, said a senior U.S. official, who, like others, spoke on the condition of anonymity to discuss the sensitive negotiations.

U.S. officials say they think North Korea is particularly incensed about South Korea’s acquisition of the F-35 fighter jet, which has stealth capabilities that would challenge the North’s radar systems.

On Friday, North Korea issued a statement saying its missile test was a “solemn warning” to “South Korean military warmongers” for their plans to hold military exercises with the United States in August and introduce “ultra modern offensive weapons,” a probable reference to the F-35.

The South Korean military said the missiles launched by the North bore similarities to the nuclear-capable, Russian-made Iskander, which probably could be used to target any part of South Korea, including the 28,500 U.S. military personnel based there.

The testing of the short-range ballistic missiles violates U.N. Security Council resolutions but not the promises Kim made to Trump at their first meeting in Singapore last June. That agreement pertained to the testing of nuclear bombs and intercontinental ballistic missiles.

Trump officials played down the launches and said they are continuing to pursue a diplomatic solution.

“They really haven’t tested missiles other than, you know, smaller ones, which is something that lots [of countries] test,” Trump told Sean Hannity of Fox News on Thursday.

Pompeo, meanwhile, also minimized the significance of the regime’s display of Kim inspecting a submarine potentially capable of launching nuclear weapons. “I went to a defense facility,” Pompeo told Fox News on Thursday. “We all go look at our militaries, and we all take pictures of them.”

North Korea’s pressure campaign began after it alleged that the United States broke an agreement made during the DMZ meeting to halt military exercises with South Korea.

“Less than a month now since the DPRK-U.S. summit meeting in Panmunjom, the U.S. is going to resume joint military exercise which it directly committed to suspend at the highest level,” the North said in a statement published by the state-run Korean Central News Agency this month.

U.S. officials denied that Trump promised to do away with the exercises completely after already sharply reducing their scope and size as part of the agreement reached in Singapore.

“I think we’re doing exactly what President Trump promised Chairman Kim we would do with respect to those exercises,” Pompeo said last week. The only U.S. officials in the room during that meeting, besides interpreters, were Trump and Pompeo.

Some U.S. officials say North Korea’s complaints about the exercises are part of a familiar strategy to wring concessions out of the United States ahead of talks.

“Everybody tries to get ready for negotiations and create leverage and create risk for the other side,” Pompeo told Bloomberg TV.

Other officials said North Korea may be trying to pressure Seoul into breaking with Washington on key issues, such as the size of future military exercises and Kim’s offer to dismantle only the Yongbyon nuclear facility in exchange for substantial sanctions relief.

Analysts said it was impossible to know for certain.

“North Korea typically has several objectives with every action and statement,” said Duyeon Kim, a Korea expert at the Center for a New American Security. “It seems Pyongyang is trying to enter negotiations from a position of strength, cancel or further shrink U.S.-South Korean drills and establish a pretext to later blame Washington if Pyongyang decides to eventually walk away from diplomacy.”

Victor Cha, a Korea expert whom the Trump administration considered to become the U.S. ambassador in Seoul, said that the various theories “are not necessarily inconsistent with each other” and that Pyongyang could be working multiple angles at the same time.

The North Korean people, however, could lose out with this strategy.

The North’s latest moves have included a decision to reject South Korea’s offer of food aid, including 50,000 tons of domestic rice, said officials familiar with the decision.

James Belgrave, a spokesman for the U.N. World Food Program, said the aid is badly needed, given estimates that 10.1 million people are experiencing food shortages in North Korea and that 1 in 5 children have stunted growth caused by malnutrition.

“It’s definitely worse than it has been in the last few years,” said Belgrave, who routinely travels to the isolated country.

Last fall, North Korea experienced its worst harvest in a decade, then a record drought this year, both of which contributed to chronic food shortages. The decision to reject the aid may derive from the country’s desire to project strength and independence ahead of the next talks.

The North’s behavior has chipped away at some of the optimism that followed Trump’s surprise meeting with Kim at the DMZ, where the two leaders shook hands and promised to renew efforts to denuclearize one of the world’s most militarized areas.

U.S. officials expressed enthusiasm for Kim’s decision to change his negotiating team, tapping the Foreign Ministry instead of his top intelligence aides, hardened military hawks whom U.S. officials viewed as arrogant and inscrutable.

Now that the Foreign Ministry is in charge of the talks, communication has increased between U.S. officials and North Koreans at Pyongyang’s diplomatic mission at the United Nations, otherwise known as the “New York Channel.” Previous discussions occurred via an intelligence channel run through the CIA.

But analysts have said the quality of the communication between the two sides is more important than its frequency.

Still, Trump appears to be willing to tolerate North Korea’s provocations in the hope that working-level talks can get the two sides closer to a denuclearization deal.

“We want to have diplomatic engagement with the North Koreans,” State Department spokeswoman Morgan Ortagus told reporters Thursday. “We urge no more provocations.”