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The release of controversial new software that allows consumers to 3D print guns has been blocked in the US just hours before it was set to be made available.

Gun access advocacy group Defense Distributed was due to put downloadable gun blueprints online on Wednesday after reaching an agreement with the Trump administration last month.

But eight states and the District of Columbia sued the government to block the settlement, arguing that the untraceable guns were a safety risk, and US District Judge Robert Lasnik in Seattle blocked the release on Tuesday.

Critics are concerned the weapons made from 3-D printers are untraceable, undetectable "ghost" firearms that pose a threat to global security.

But some gun rights groups said the technology is expensive, the guns are unreliable and the threat is being overblown. The publication of the files is now illegal under federal law, Lasnik said.

"There are 3-D printers in public colleges and public spaces and there is the likelihood of potential irreparable harm," Lasnik said at the end of a one-hour hearing on the lawsuit.

Speaking before the decision was made, US leader Donald Trump said the release "didn't make much sense".

In a tweet on Tuesday, he said: "I am looking into 3-D Plastic Guns being sold to the public. Already spoke to NRA, doesn’t seem to make much sense!"

Josh Blackman, a lawyer for the company Defense Distributed, said during Tuesday's hearing that blueprints had already been uploaded to the firm's website on Friday.

Blackman said in an interview he was disappointed in the court's ruling and the judge's comment.

"Mr. Wilson scrupulously obeys all court orders," Blackman said, adding that he was awaiting the judge's written order before deciding on further legal action.