CAPE CANAVERAL, Fla. >> In the latest setback to return astronauts to the moon, NASA delayed the highly anticipated flight yet again after a new problem cropped up with the rocket Saturday.

April is now the earliest that the four Artemis II astronauts could fly to the moon.

NASA revealed the latest problem just one day after targeting March 6 for Artemis II, humanity’s first flight to the moon in more than half a century.

Overnight, the flow of helium to the rocket’s upper stage was interrupted, officials said. Solid helium flow is essential for purging the engines and pressurizing the fuel tanks.

This helium issue has nothing to do with the hydrogen fuel leaks that marred a countdown dress rehearsal of the Space Launch System rocket earlier this month and forced a repeat test.

NASA Administrator Jared Isaacman said a bad filter, valve or connection plate could be to blame for the stalled helium flow. Regardless of the cause, he said, the only way to access the area and fix the problem is to return the 322-foot rocket to its hangar for repairs.

“We will begin preparations for rollback, and this will take the March launch window out of consideration,” Isaacman said via X. NASA’s next opportunities would be at the beginning or end of April.

Earlier in the day, NASA said it was preparing to move the rocket back to the Vehicle Assembly Building at Kennedy Space Center while raising the possibility of the work being done at the pad.

The situation is dynamic, said spokeswoman Cheryl Warner. Whether the fixes are at the pad or in the hangar, the rollback preparations alone rule out any chance of making a March launch, she said.

Hydrogen fuel leaks had already delayed the Artemis II lunar fly-around by a month. A second fueling test on Thursday revealed hardly any leaks, giving managers the confidence to aim for a March liftoff. The four astronauts went into their two-week quarantine Friday evening, mandatory for avoiding germs.

— The Associated Press