The US's National Security Agency, the electronic eavesdropping body, has disclosed that its telephone and internet data collection is far greater than previously known in the face of unusually sharp congressional questioning.
The disclosures, and the more aggressive stance from members of the House judiciary committee, underlined how the NSA is losing support in a Congress which had initially largely backed the White House's defense of anti-terror surveillance.
(Read More: Putin seeing signs of Snowden shifting on the US)
John Inglis, a deputy director of the agency, told a congressional panel that the NSA collected the data of not only people whom suspected foreign terrorists were talking to in the US, as they say they are authorized by law to do.
Mr Inglis, using the NSA's in-house jargon, said the agency could go "two or three hops" beyond, to the person originally contacted by the target, and to people they had contacted, and then one step further.
The NSA has previously said it traces connections with potential terror targets by only two degrees of separation.
Members of the committee said the NSA had gone beyond the law in their surveillance operations and indicated they may no longer be able to support the authorization of some of its powers.
The debate over the NSA has been sparked by leaks from the former NSA contractor, Edward Snowden, now at Moscow Airport as he waits to find asylum in the numerous countries he has applied to.
(Read More: Snowden emerges at airport, seeks temporary asylum in Russia)
Jim Sensenbrenner, a Republican from Wisconsin who helped author the original post 9/11 Patriot Act under which the NSA collects information on potential terrorists, said parts of the legislation would not be renewed in 2015 unless Congress' concerns were satisfied.
"Unless you realize that you've got a problem, you are not going to have it any more," he told James Cole, the deputy attorney-general.
At the hearing, which also heard from the FBI and the Justice Department, officials again justified the surveillance programm by pointing to successes in preventing terror attacks inside the US.
Read more from the Financial Times
"This is not done in some rogue manner – we know of no one who has abused this in a way that would have caused (them to be) disciplined," said Mr Cole.
The committee's senior Democrat, John Conyers, of Michigan, said: "You've already violated the law in my opinion."
The Republican committee chair, Bob Goodlatte, who has been largely supportive of the NSA's surveillance, asked if the government had really thought its massive surveillance program could be kept secret from the American people.
"Well, we tried," said Robert Litt, the general counsel for the Director of National Intelligence, to laughs from the audience.