ISTANBUL — Jared Kushner, President Trump’s son-in-law and senior adviser, met with the Saudi king and crown prince during a tour of the Middle East to try to build momentum for his long-awaited plan for peace between Israel and the Palestinians, the White House said in a statement on Wednesday.

The meeting, held on Tuesday, was Mr. Kushner’s first face-to-face encounter with Crown Prince Mohammed bin Salman, the day-to-day ruler of Saudi Arabia, since Saudi agents killed the dissident Jamal Khashoggi in Istanbul in October.

The Trump administration has stood by Prince Mohammed, who has forged a strong relationship with Mr. Kushner, even after American intelligence agencies concluded that the prince most likely ordered the killing.

The White House statement did not mention Mr. Khashoggi, a Saudi citizen who lived in Virginia. His killing has tarnished Prince Mohammed’s reputation and spurred efforts in Congress to punish the kingdom. The White House issued its statement a day after the meeting took place, as public attention was dominated by congressional testimony by Michael D. Cohen, Mr. Trump’s former fixer.