Collins said that many experts consider the moon as a gateway to Mars, but that he stands with the minority view that going to Mars should be the priority.
Trump's exact meaning was uncertain, but he may have been urging the U.S. space agency to put more of a focus on the voyage to Mars, with the Moon serving as just a stepping stone.
The president made the comment in a tweet while aboard Air Force One en route from Ireland to Washington, D.C.
Today's presidential tweet came amid deep discussions over how much it will cost to accelerate NASA's moon exploration program, now known as Artemis, and make the 2024 deadline for putting the next man and the first woman on the lunar surface.
The accelerated timetable for going to the moon was a key recommendation in March of the new National Space Council led by Vice President Mike Pence. "It marks a first step in returning American astronauts to the moon for the first time since 1972, for long-term exploration and use".
The NASA website also provided details on the space agency's plans for making the moon a jumping off point for future missions to Mars and a place to test equipment and technology for other forays out into the solar system. Ladies and gentlemen, that's just not good enough.
"Under my Administration, we are restoring @NASA to greatness and we are going back to the Moon, then Mars", he tweeted. Those plans stem directly from a Trump administration Space Policy Directive 1 the president signed in late 2017. "I am updating my budget to include an additional $1.6 billion so that we can return to Space in a BIG WAY!"
Mars acquires the Moon and a satellite to be named later from Earth in exchange for Phobos, Deimos, and an asteroid.
When asked about the tweet, a NASA media relations specialist pointed CNET to a response tweet by NASA administrator Jim Bridenstine.
There are probably some frantic emails flying between NASA headquarters and the White House right now.