JEJU, South Korea — When North Korea launched a volley of projectiles off its east coast on Saturday, it sought to escalate the pressure on President Trump to return to the negotiating table with a compromise on easing sanctions, analysts said, by signaling that it could scuttle his biggest diplomatic achievement with the North.

Saturday’s weapons tests were the most serious by the North since the country launched its Hwasong-15 intercontinental ballistic missiles in November 2017. Although North Korea has not gone so far as to renege on its moratorium on nuclear and ICBM tests, which its leader, Kim Jong-un, announced last year, the Saturday launch indicated that Mr. Kim was toying with the idea of lifting the moratorium, analysts said.

[Update: North Korea fired a projectile on Thursday. The launch was its second weapons test in less than a week.]

Mr. Trump has repeatedly described the moratorium as his biggest achievement on North Korea, citing it as proof that his diplomacy with Mr. Kim has been working. The leaders have met twice: first in Singapore in June and again in Hanoi, Vietnam, in February.