Just minutes before he was scheduled to meet President Xi Jinping of China, the president threatened on social media to resume nuclear testing “on an equal basis” with other countries.

The highly anticipated event covered a lot of ground on tariff and trade barriers, but questions remain about reaching a lasting accord.

Beijing has been expanding its arsenal, and distrust between China and the United States over nuclear weapons has deepened, with little hope of an agreement.

© Haiyun Jiang/The New York Times

The two leaders reached an agreement on fentanyl, some tariffs and rare earths, at least for a year. But even as the global trade picture cleared a little, Mr. Trump spurred new worries about nuclear proliferation.

© Haiyun Jiang/The New York Times

The two leaders reached an agreement on fentanyl, some tariffs and rare earths, at least for a year. But even as the global trade picture cleared a little, Mr. Trump spurred new worries about nuclear proliferation.

Plus, goodbye to “milk chocolate”?

© Haiyun Jiang/The New York Times

Just minutes before he was scheduled to meet President Xi Jinping of China, the president threatened on social media to resume nuclear testing “on an equal basis” with other countries.

© Kadielle Shaw/U.S. Space Force, via AFGSC

The test comes days after President Vladimir V. Putin announced the previous trial of another Russian nuclear weapon.

© Pool photo by Alexander Zemlianichenko