President Trump and North Korean leader Kim Jong Un abruptly cut short their two-day summit Thursday after they were unable to reach an agreement to dismantle Pyongyang’s nuclear weapons.

Talks collapsed unexpectedly amid a disagreement about economic sanctions, with the two leaders and their delegations departing their meeting site in Vietnam’s capital without sitting for a planned lunch or participating in a scheduled signing ceremony.

Kim said he was prepared in principle to denuclearize, and Trump said an agreement was “ready to sign.” But Trump said the main impediment to a deal was Kim’s requirement that the United States lift all economic sanctions on North Korea in exchange for the closure of only one nuclear facility, which still would have left Pyongyang with a large arsenal of missiles and warheads.

“We had some options, but at this time we decided not to do any of the options,” Trump said. He added, “Sometimes you have to walk, and this was just one of those times.”

For Trump, the surprising turn of events amounted to a diplomatic failure. The president flew 20 hours to Vietnam with hopes of producing demonstrable progress toward North Korea’s denuclearization, building upon his first summit with Kim last summer in Singapore.

The breakdown sent shivers through financial markets in Asia, with South Korea’s stock market falling sharply just before the close of trading, to end down 1.8 percent. The South Korean won also slipped, and Japan’s main Nikkei 225 share index ended down 0.8 percent.