The Trump administration has broken its long silence on a high-profile National Security Agency programme that sifts records of Americans’ telephone calls and text messages in search of terrorists on Thursday.

They acknowledged for the first time that the system has been indefinitely shut down — but asked congress to extend its legal basis anyway.

In a letter to congress delivered on Thursday and obtained by The New York Times, the administration urged lawmakers to make the USA Freedom Act permanent, being the legal authority for the National Security Agency to gain access to logs of Americans’ domestic communications.

The law, enacted after the intelligence contractor Edward Snowden revealed the existence of the programme in 2013, is set to expire in December, but the Trump administration wants it made lasting.

The unclassified letter, signed by Dan Coats on Wednesday in one of his last acts as the director of National Intelligence, also conceded that the NSA has indefinitely shut down that programme after recurring technical difficulties repeatedly caused it to collect more records than it had legal authority to gather.

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That fact has previously been reported, but the administration had refused to officially confirm its status.

“The National Security Agency has suspended the call detail records programme that uses this authority and deleted the call detail records acquired under this authority,” Mr Coats wrote.

“This decision was made after balancing the programme’s relative intelligence value, associated costs, and compliance and data integrity concerns caused by the unique complexities of using these company-generated business records for intelligence purposes.”

Complicating matters, three other surveillance authorities primarily used by the FBI are also set to expire in mid-December.

They include provisions that let investigators get court orders to collect business records relevant to a national security investigation, wiretap “lone wolf” terrorists without links to a foreign power, and keep wiretapping someone suspected of being a spy or a terrorist who switches phone lines in an effort to evade surveillance.

The NSA’s ability to gain access to and analyse Americans’ domestic calling records traces back to the aftermath of the 9/11 terrorist attacks, when the Bush administration set up its then-secret Stellarwind programme, a basket of surveillance and bulk data collection activities that relied on a raw claim of executive power to bypass legal constraints.