NASA's Orion project, set to be the first manned spacecraft to send man to Mars, may not launch until 2023, the U.S. space agency said Wednesday.

A test flight of Orion with humans on board was estimated to happen in 2021, but officials say that they now have less confidence in this date, according to BBC News.

The current goal for engineers and technicians is still set for 2021, but there is doubt among administrators.

"We did some changes to reduce weight, took a lot of weight out of the structure for EM-1 and EM-2,  and reduced the number of cone panels that make up the cone section of the Orion," said Bill Gerstenmaier, associate administrator for human exploration at NASA, The Verge reported.

Other factors included in the delay of the project are equipment use, structural changes and software development.

"We're not seeing any issues in those areas, but we have to account for those, because we have a lot of runway in front of us," NASA Associate Administrator Robert Lightfoot told reporters during a teleconference, according to Space.com.

Lightfoot added that the delay is also a result of the U.S. president's budget request for NASA.

Despite the anticipated delay, NASA assures that it is still making progress in terms of exploration programs that will bring humans farther into space, AFP reported.