NASA goal to snag an asteroid and bring a space rock close to Earth is a distraction from the effort to send humans to Mars, a top asteroid expert says.

In a commentary in the journal Nature, planetary scientist Richard Binzel of the Massachusetts Institute of Technology calls NASA’s Asteroid Redirect Mission (a.k.a. ARM) “a multibillion-dollar stunt.” The strongly worded text comes after a National Research Council report in June offered multiple routes to get to Mars, including the asteroid-snagging plan, but didn’t recommend one over any other.

Binzel, whose work has helped to evaluate the hazard from various near-Earth asteroids, said it’s time to choose an option that doesn’t detract from the ultimate goal of reaching the Red Planet.

“Over the next two months, Obama’s 2015 budget will be shaped. NASA needs to make a clear choice about its priorities,” Binzel wrote. “It should abandon the ARM mission concept and make an asteroid survey its top priority to provide a basis for future crewed missions.”

The administration has set goals to send astronauts to an asteroid by 2025 and to Mars by the mid-2030s. But trying to retrieve part of an asteroid is a waste of resources, Binzel argued.