Although some foreign policy analysts were heartened that Kim appeared eager to set a positive tone for his summit with Trump, which could come in late May or early June, Trump aides were less enthused. In their view, Kim’s moves aimed to offer relatively modest pledges — which could be quickly reversed — to create the “illusion” that he is “reasonable” and willing to compromise.

That, the Trump aides said, would make it more politically difficult for the United States to reject the North’s demands.

Kim’s announcement early Saturday in Pyongyang surprised White House officials, who had been anticipating a statement to the North Korean people in advance of a summit with Trump but did not know when or how he would deliver it.