Secretary of State Marco Rubio arrived on Monday in Saudi Arabia for the second leg of a whistle-stop Middle East tour to discuss the future of both Gaza and Ukraine amid criticism that the Trump administration was acting without consulting relevant foreign partners about the wars in both countries.

Mr. Rubio, who flew to Riyadh from Israel, was expected to press the Saudi leadership to propose a vision for postwar Gaza. President Trump’s idea to depopulate and occupy the territory has spurred widespread opposition in the Arab world, including in Saudi Arabia. That has led Mr. Rubio and other U.S. officials to encourage Arab leaders to suggest an alternative.

Mr. Rubio is also scheduled to meet in Riyadh with Russian officials to discuss the future of the Russia-Ukraine war. They are expected to be joined by two other key U.S. officials — Mike Waltz, the national security adviser, and Steve Witkoff, Mr. Trump’s Middle East envoy, who also works on Ukraine-Russia issues.

In addition to angering Arab allies with his contentious proposal for Gaza, Mr. Trump frustrated partners in Europe when he spoke last week unilaterally with President Vladimir V. Putin of Russia about Ukraine’s future. His administration has also said that European governments will play no role in future talks, despite the conflict taking place within Europe’s borders.

The moves prompted concern in Ukraine and elsewhere in Europe, where leaders fear being sidelined from discussions that will dictate their countries’ futures. Volodymyr Zelensky, the Ukrainian president, reiterated in an interview that aired on Sunday that his country would “never” accept a peace deal struck by the United States and Russia if Ukraine was not involved in the talks.