NASA wants to grab a small asteroid and tow it into orbit around the moon, as part of a long-range plan towards establishing permanent manned outposts in space, according to a US senator.

To get the project off the ground, US President Barack Obama will propose around $100 million for the US space agency in his 2014 budget, which he submits to Congress on Wednesday, Senator Bill Nelson said in a statement.

"This is part of what will be a much broader program," the Florida Democrat explained.

"The plan combines the science of mining an asteroid, along with developing ways to deflect one, along with providing a place to develop ways we can go to Mars."

The plan calls for a robotic-spacecraft to capture the asteroid and tow it back towards Earth, ultimately leaving it in a stable orbit around the moon, close enough that, within eight years, astronauts could head on over.

A similar plan was initially proposed in 2012 by experts at the California Institute of Technology, and the group, along with other top researchers in the field, have since prepared a detailed study into the project's feasibility.

"It would be mankind's first attempt at modifying the heavens to enable the permanent settlement of humans in space," scientists said in their report.

Obama's goal of sending a manned mission to a near-Earth asteroid by 2025 is impossible given NASA's current and projected funding levels, expert analysis has suggested.

But using an unmanned vehicle to instead bring a 500-ton asteroid close to home could change the game and get humans to an asteroid as early as 2021, four years ahead of the deadline.

Once there, "there could be mining activities, research into ways of deflecting an asteroid from striking Earth, and testing to develop technology for a trip to deep space and Mars," Nelson's statement said.