LONDON — In his first solo trip to the broader Middle East as President Trump’s designated peacemaker, Jared Kushner has found both cause for optimism and reminders of just what a daunting task his father-in-law has given him.

Over the course of two days, he met with leaders from several influential Arab countries and emerged encouraged by their stated eagerness to help him bring Israelis and Palestinians together. But his visit on Wednesday with President Abdel Fattah el-Sisi of Egypt showed how other issues can easily complicate the initiative as both sides sought to paper over a dispute over American aid.

Just a day earlier, the United States cut or delayed nearly $300 million in aid to Egypt, a symbolic blow to a strategic relationship that has been a pillar of American policy in the Middle East for almost four decades. It was also a sign of growing impatience on the part of Secretary of State Rex W. Tillerson, who does not share Mr. Trump’s affinity for Mr. Sisi.

Mr. Kushner was caught out by bad timing — his trip to Egypt had been fixed weeks earlier and officials said the aid decision was driven by schedules unrelated to his travels. Mr. Sisi and Mr. Kushner gave no public hint of discord as they grinned and shook hands for the benefit of news photographers; Mr. Sisi’s office later issued a lengthy statement praising relations between the two nations.