Updated 11:30 p.m. Eastern with revised Roscosmos plan.

WASHINGTON — A rare uncrewed flight of a Soyuz spacecraft took another twist Aug. 24 when the spacecraft failed to make an automated docking with the International Space Station.

The Soyuz MS-14 spacecraft was scheduled to dock with the station’s Poisk module at about 1:30 a.m. Eastern. While the spacecraft’s initial approach to the station took place normally, the spacecraft failed to make a final approach for docking, remaining about 90 meters from the station.

NASA said in a later statement that the station’s two Russian cosmonauts, overseeing the docking, issued a command to abort the docking at 1:36 a.m. Eastern, directing the Soyuz to move away from the station. The ISS, NASA added, was never in danger during the aborted docking attempt.

The problem, Russian flight controllers said, appears to be a problem with the Kurs automated docking system on the ISS, and not a problem with the Soyuz spacecraft itself. Roscosmos, in a brief statement after the aborted docking, said that the agency’s leader, Dmitry Rogozin, chaired a meeting to discuss the problem and determine what to do, but provided few additional details about the problem.

Original plans called for cosmonauts Alexey Ovchinin and Alexander Skvortsov to replace a signal amplifier unit on the Kurs over the weekend, and prepare for another docking attempt Aug. 26. However, in a series of English-language tweets later in the day Aug. 24, Roscosmos said the next docking attempt will be pushed back to Aug. 27.

Instead, Skvortsov will board the Soyuz MS-13 spacecraft currently docked to the station’s Zvezda module Aug. 26 and manually dock it to the Poisk module. That will free up the Zvezda module’s port for a new docking attempt by Soyuz MS-14. “The situation is complicated, however [it] is under control,” Roscosmos stated.

The delayed docking doesn’t pose an issue for the station or its crew, in part because this Soyuz spacecraft carried no one on board. The flight, the first uncrewed Soyuz spacecraft flight since the Soyuz TM-1 mission to the Mir space station in 1986, was intended to test the use of the Soyuz-2.1a launch vehicle for launching Soyuz spacecraft, as Russia seeks to phase out the older Soyuz-FG rocket that it has been using for crewed missions by 2020.

The Soyuz-2.1a, used for satellite launches as well as some Progress cargo missions, has a new digital flight control system and upgraded engines. The launch, at 11:38 p.m. Eastern Aug. 21 from the Baikonur Cosmodrome, was a success.

The mission also provided an opportunity to test changes to the Soyuz spacecraft itself, including improvements to its navigation system and descent control system. Those systems did not appear to be at fault in the aborted docking.

While there are no astronauts on the Soyuz MS-14, it does have a passenger or sorts: a humanoid robot known alternatively as FEDOR or Skybot F-850. Roscosmos plans to test the ability of the robot to support cosmonauts on the ISS during a relatively short stay on the station, before Soyuz MS-14 returns to Earth in early September.