The highly anticipated launch of China’s robotic Chang’e-7 mission, designed to scour the moon’s south pole for water ice — a highly valuable resource that the US also hopes to use — “cannot take place during the planned window this year,” according to a statement from the China Manned Space Engineering Office shared by Chinese state media.

Takeoff of the mission had been expected to occur as soon as Sunday evening, or Monday morning Beijing time. It’s not clear how soon China may be able to attempt to get the mission off the ground.

The precise reason for the delay was not immediately clear. State media said only that the “lunar probe does not meet launch conditions,” and the “assessment was conducted following the principle of prudence, reliability and absolute mission success.”

Both the United States and China are raching to build settlements on the moon’s south pole, where water is believed to exist in frozen abundance inside shadowy craters.

No mission has yet directly analyzed water on the moon, as Chang’e-7 will attempt to do.