A key SpaceX Starship Super Heavy rocket launch test now is likely to take place later this month rather than sometime this week, the space company's CEO Elon Musk said on Monday.

SpaceX envisions Starship as a fully reusable transportation system to carry astronauts and cargo to Earth orbit, the moon, Mars and beyond. The rocket is scheduled to lift off from SpaceX's Starbase facilities at Boca Chica in South Texas in the first launch of the company's fully stacked 120-meter-tall Starship rocket system. Fully stacked means all its parts are assembled, with the upper stage sitting atop the booster.

"Starship launch trending towards near the end of third week of April," Musk wrote on Twitter a day after stating that it was ready for launch and "awaiting regulatory approval."

A planning notice posted by the Federal Aviation Administration (FAA) on April 4 said the launch's primary expected date was for Monday, but listed backup dates as Tuesday and Wednesday of this week. Musk said last week Starship would be ready to launch this week.

The FAA on Monday issued a revised notice that said the launch could now happen April 17.

SpaceX must still get a launch license from the FAA for what is expected to be its first orbital flight test from Boca Chica. One key hurdle remains – completion of a federal environmental compliance review.

The Starship rocket system consists of a Starship rocket sitting atop a "Super Heavy" first stage booster with 33 rocket engines. The plan is to deploy the Starship second stage into space, where it would complete a full orbit of Earth before re-entering the atmosphere and splashing down off the coast of Hawaii. The plan also would be for the Super Heavy booster to land in Texas near the launch site.