According to the space agency, the delay is designed to give it more time to evaluate the bidders' proposals and to "preserve the ability to seamlessly transition" from the development phase, but it may not need the full extension period and could award the lander contracts earlier. 

The extension also gives the companies more time to design and develop their lander systems, NASA said. 

Elon Musk's SpaceX, a team of aerospace giants led by Jeff Bezos' Blue Origin and Leidos-owned Dynetics won a combined $967 million in seed funding from NASA last year to develop rival concepts for a human lunar landing system, The Verge reported on Sunday. 

A delay was also expected as US President Joe Biden's team holds off on releasing any space policy, keeping the long-term fate of NASA's Artemis programme uncertain. 

It's the space agency's first effort to spend money on astronaut moon landers since the Apollo programme in the 1970s, the report said. 

SpaceX's lunar lander pitch to NASA is Starship, a roughly 16-storey tall fully reusable vehicle the company has been launching and landing in short, suborbital test flights -- called "hops" -- in Boca Chica, Texas. The company's chunk of development funds was $135 million. 

Jeff Bezos' Blue Origin got the largest award, $579 million, to develop its Blue Moon lander. The company announced a "National Team" in 2019 comprising of Lockheed Martin, Northrop Grumman and Draper to work on the project. Dynetics got $253 million for its lander and has partnered with Sierra Nevada Corp. 

Last week, NASA told the three contractors that an extension to their development contracts "will be required". 

Under the Trump administration's timeline, the agency had planned to pick two of the three bidders in late February, giving a stamp of approval for two systems that would inevitably carry humans to the moon. 

The Biden administration is yet to pick its NASA administrator or release any space policy objectives, but is expected to slow down the Artemis programme's sprint to the moon by 2024 -- a date widely viewed as unrealistic.