NASA's closeout crew has departed the launch pad after finishing its White Room procedures.

Currently, only the Artemis II astronauts -- Christina Koch, Reid Wiseman, Victor Glover Jr. and Jeremy Hanse -- remain in the Orion spacecraft at the top of the SLS rocket, ready for launch.

-ABC News' Briana Alvarado

NASA teams are troubleshooting an issue with the temperature of one of the batteries on the Launch Abort System.

NASA is reporting that the temperature is out of range for one of the two batteries. The agency says it is not a constraint for launch currently, but it will be if the issue continues when the temperature is checked during the final countdown minutes.

"Engineers investigated a sensor on the launch abort system’s attitude control motor controller battery that showed a higher temperature than would be expected. It is believed to be an instrumentation issue and will not affect today’s launch," the agency said in a statement.

-ABC News' Briana Alvarado

Transportation Secretary Sean Duffy said the Artemis II moon mission is "critically important" a few hours ahead of the scheduled launch.

"This is a moment that brings the country together," Duffy told Gio Benitez on ABC News Live.

"The technology, the time, the effort that has gone into making today possible is so cool," he added.

Duffy said the U.S. is in a race against China to get to the moon's South Pole. Currently, Artemis III is planned for 2028, while China’s space program is gearing up for a moon landing by 2030.

"There was a time that the adage was, ‘He who controls the seas controls the world.' Now it is, 'He who will control space will control the world,'" Duffy said. “We have to win. This is critically important."

NASA said it has resolved the Flight Termination System issue, adding it is "no longer a constraint" and is proceeding with countdown operations.

The issue affected the rocket, not the Orion spacecraft. The FTS is a signal to blow the rocket up if it starts heading in a direction that would endanger lives.

Orion would have separated from the rocket safely, and the rocket would be issued a command to self-destruct.

Additionally, the Launch Abort System hatch is now also closed. The closeout crew successfully closed both hatches on Orion, concluding the hatch preparation and closure phase of launch operations.

-ABC News' Briana Alvarado and Gio Benitez

NASA says the Artemis II return is on track, with teams focused on the final phase of the mission: the reentry, splashdown and recovery sequence.

From the moment Orion enters Earth’s atmosphere to the time it splashes down in the Pacific Ocean, the entire sequence takes about 13 minutes.

“It’s 13 minutes of things that have to go right,” NASA Flight Director Jeff Radigan said during the final mission status briefing, adding that in his view, “it’s more, in my head, about an hour and a half of things that have to go right.”

Officials also addressed public visibility of entry and splashdown along the West Coast. Based on the planned trajectory, Radigan said, “I don’t expect it to be visible for the folks in California,” noting that the spacecraft will be targeting a landing area well offshore.

He cautioned the public to stay clear of the area, pointing to the debris that is expected to fall.

NASA confirmed a small leak in the service module’s oxidizer system, but officials said it will not affect the return.

-ABC News' Briana Alvarado