Mr. Trump is scheduled to meet President Xi Jinping of China on Saturday. A core American grievance is Chinese cyberespionage against the U.S., which has accelerated sharply over the past year, intelligence officials and analysts say. Trade conflicts and other tensions have also strained relations between the world’s two largest economies.

News analysis: Russia’s seizure of three Ukrainian ships has complicated Mr. Trump’s plan to meet with President Vladimir Putin of Russia this weekend.

Two little words send U.S. markets rising

The Federal Reserve chairman, Jerome Powell, said on Wednesday that the central bank’s benchmark interest rate was “just below” the neutral level, raising investors’ hopes that the Fed might soon end its push to drive up rates.

The announcement sent stocks up 2.3 percent, erasing this month’s losses. Analysts, however, warned that investors were overreacting and that there was little evidence in the rest of Mr. Powell’s speech that indicated a change in plans.