NASA is developing an Asteroid Redirect Mission (ARM) — a first-ever mission to identify, capture and redirect an asteroid to a safe orbit of Earth’s moon for future exploration by astronauts in the 2020s.

ARM will use capabilities in development, including the new Orion spacecraft and Space Launch System (SLS) rocket, and high-power Solar Electric Propulsion. All are critical components of deep-space exploration and essential to meet NASA’s goal of sending humans to Mars in the 2030s. The mission represents an unprecedented technological feat, raising the bar for human exploration and discovery, while helping protect our home planet and bringing us closer to a human mission to one of these intriguing objects.

via Responding to Potential Asteroid Redirect Mission Targets | NASA.

Here is an article from 12/24/2012 about this.