US space agency NASA on Wednesday said it will soon recruit new astronauts as part of its efforts to prepare for an eventual manned mission to Mars.

"This next group of American space explorers will inspire the Mars generation to reach for new heights, and help us realize the goal of putting boot prints on the Red Planet," NASA Administrator Charles Bolden said in a statement, Xinhua reported.

NASA said these astronauts may fly on any of four different US vessels during their careers: the International Space Station, two commercial crew spacecraft currently in development by US companies and NASA's Orion deep-space exploration vehicle that will take humans to Mars in the 2030s.

Those who want to apply must be US citizens "with a wide variety of backgrounds", including pilots, engineers, scientists and medical doctors.

The requirements include a bachelor's degree from an accredited institution in engineering, biological science, physical science or mathematics.

The candidates should also have at least three years of related professional experience or at least 1,000 hours of pilot-in-command time in a jet aircraft.

Additional requirements included the ability to pass the NASA long-duration spaceflight physical, which required would-be astronauts to have a height between 62 inches (1.57 meters) and 75 inches (1.90 meters).

The space agency said it will accept applications from 14 December through mid-February and expects to announce candidates selected in mid-2017.

To date, NASA has selected more than 300 astronauts to fly space missions. At the moment, there are 47 people in the active astronaut corps.