NASA has completed the giant rocket that will take US astronauts back to the Moon, the space agency's head announced Monday, pledging the mission would take place in 2024 despite being beset by delays.

Towering 212 feet (65 meters), the equivalent of a 20-story building,

The Space Launch System (SLS) is the tallest rocket ever built at a towering 212 feet (65 meters), the equivalent of a 20-story building.

It is also the most powerful, designed to reach a record-breaking speed of Mach 23 before separating from its upper stage, the Orion crew capsule. But its development has been hit by delays and cost overruns - its first flight was set to take place in November 2018, and its price tag has risen from $6.2 billion to $8 billion, or 29 percent, according to a June audit report. Standing before the orange behemoth at the Michoud Assembly Facility in New Orleans, NASA administrator Jim Bridenstine called it a "very important day" for the space agency "when we get to announce core stage complete for in fact the SLS rocket.