WASHINGTON — The White House tried to swat away criticism Friday that the U.S. is getting nothing in exchange for agreeing to a historic face-to-face summit between President Donald Trump and North Korean leader Kim Jong Un.

White House press secretary Sarah Huckabee Sanders said North Korea has made promises to denuclearize, stop its nuclear and missile testing and allow joint U.S.-South Korean military exercises. But questions remained over exactly what North Korea means by “denuclearize” and what the U.S. might be risking with a highly publicized summit that will build up Kim’s stature among world leaders.

“Let’s not forget that the North Koreans did promise something,” Sanders said, responding to a reporter’s question about why Trump agreed to a meeting — unprecedented between leaders of the two nations — without preconditions.

She added: “We are not going to have this meeting take place until we see concrete actions that match the words and the rhetoric of North Korea.”

Still, the White House indicated that planning for the meeting was fully on track.

The previous night’s announcement of the summit marked a dramatic turnaround after a year of escalating tensions and rude insults between the two leaders. A personal meeting would have been all but unthinkable when Trump was being dismissed as a “senile dotard” and the Korean “rocket man” was snapping off weapons tests in his quest for a nuclear arsenal that could threaten the U.S. mainland.

North Korea’s capabilities are indeed close to posing a direct atomic threat to the U.S. And the wider world has grown fearful of a resumption of the Korean War that ended in 1953 without a peace treaty.

The prospect of the first U.S.-North Korea summit has allayed those fears somewhat. The European Union, Russia and China — whose leader spoke by phone with Trump on Friday — have all welcomed the move.

North Korea’s government has yet to formally comment on its invitation to Trump. South Korea said the president agreed to meet Kim by May, but Sanders said Friday that no time and place had been set.

The “promises” on denuclearization and desisting from weapons tests were relayed to Trump by South Korean officials who had met with Kim Monday and brought his summit invitation to the White House. Trump discussed the offer with top aides on Thursday. Some expressed their reservations but ultimately supported the president’s decision to accept it, according to U.S. officials who were briefed on the talks and requested anonymity to discuss them.

Still, some lawmakers and foreign policy experts voiced skepticism about the wisdom of agreeing to a summit without preparations by lower-level officials, particularly given the lack of trust between the two sides. North Korea is also holding three American citizens for what Washington views as political reasons.

“A presidential visit is really the highest coin in the realm in diplomacy circles,” said Bruce Klingner, a Korea expert at the conservative-leaning Heritage Foundation, adding that Trump “seemed to spend it without getting anything in return, not even the release of the three U.S. captives.”

Some say Trump could be setting himself up for failure amid doubts over whether Kim has any intention to relinquish a formidable atomic arsenal that he has made central to his personal stature and North Korea’s standing in the world. Kim would also boost his own standing by becoming the first of the three hereditary leaders of North Korea to sit down with an American president.

Evans Revere, a former senior State Department official experienced in negotiating with North Korea, warned there is a disconnect between how the North and the U.S. describes “denuclearization” of the divided Korean Peninsula. For the U.S. it refers to North Korea giving up its nukes; for North Korea it also means removing the threat of American forces in South Korea and the nuclear deterrent with which the U.S. protects its allies in the region.