The Liverpool midfielder is struggling with a foot injury and was not involved in any full training sessions at Japan's pre-tournament camp in Mexico.
Endo took part in running and passing drills with his teammates on Monday after moving to their World Cup base in Nashville, and Moriyasu said he was still in contention to face the Dutch in Dallas.
"According to the medical reports, there is nothing to say that he can't play," Moriyasu, whose team also play Sweden and Tunisia in Group F, told reporters before leaving Mexico.
"So we just believe, pray and wait."
Endo suffered a season-ending foot injury playing for Liverpool against Sunderland in February and returned for Japan in a 1-0 friendly win over Iceland in Tokyo on May 31st.
He came off at half-time and has continued to feel discomfort.
Moriyasu said replacing the 33-year-old in his squad was an option if he was not able to play a part in the tournament.
"I'm always considering replacements if a player can't play, and that doesn't just go for Endo but for everyone.
"We have several players returning from injury and we need to keep assessing them until the last minute, but we called them up with the assumption that they would be fit in time."
Brighton winger Kaoru Mitoma was left out after injuring his hamstring less than a week before Moriyasu named his squad.
Monaco's Takumi Minamino also missed out after tearing the anterior cruciate ligament in his left knee in December.
FIFA World Cup 2026
The 2026 World Cup will be held from June 11th to July 19th in the United States, Canada and Mexico. The tournament will feature 48 national teams and will be played in 16 modern stadiums.
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