The White House has rejected a petition to build a Death Star - a huge battle-station armed with a superlaser as seen in the Star Wars films.
In a playful response, a senior US government official said the Obama administration "does not support blowing up planets".
The official also said the cost - about $850 quadrillion - was too high.
More than 34,000 people had signed the petition, saying the project would spur job creation and strengthen defence.
They also wanted the government to begin construction by 2016.
The White House is obliged to respond to all petitions that gain more than 25,000 signatures.
'Force be with us!'
Responding to the petition, Paul Shawcross, head of the administration's budget office on science and space, admitted in a blog that "a Death Star isn't on the horizon".
"However, look carefully and you'll notice something already floating in the sky - that's no Moon, it's a Space Station!
Mr Shawcross was referring to the International Space Station, which currently has six people on board.
And he ended his blog with an appeal to the signatories of the petition: "If you do pursue a career in a science, technology, engineering or math-related field, the Force will be with us!
"Remember, the Death Star's power to destroy a planet, or even a whole star system, is insignificant next to the power of the Force."