The legal authority for US spy agencies to bulk-collect Americans’ phone data has expired, after the Senate failed to reach a deal.
Republican presidential hopeful Rand Paul blocked a Patriot Act extension and it lapsed at midnight (04:00 GMT).
However, the Senate did vote to advance the White House-backed Freedom Act so a new form of data collection is likely to be approved in the coming days.
The Freedom Act imposes more controls, after revelations by Edward Snowden.
The former National Security Agency (NSA) contractor first exposed the extent of the data collection in 2013.
The White House described the expiry of the deadline as an “irresponsible lapse” by the Senate.
“On a matter as critical as our national security, individual senators must put aside their partisan motivations and act swiftly. The American people deserve nothing less,” it said in a statement.
The failure to reach a deal means that security services have temporarily lost the right to bulk-collect Americans’ phone records, to monitor “lone wolf” terror suspects and to carry out “roving wiretaps” of suspects.
The government can still continue to collect information related to any foreign intelligence investigations.
Analysts also said there could be workarounds to allow continued data collection in some cases. Authorities could try to argue that older legal provisions – so-called grandfather clauses – still apply.
A Senate vote on the Freedom Act can come no earlier than 05:00 GMT yesterday.
The Freedom Act retains most of the Patriot provisions, but requires that records must be held by telecommunications companies, and that the NSA needs court approval to access specific information. It also explicitly prohibits bulk collection of data.
The NSA, which runs the majority of surveillance programmes, stopped collecting the affected data at 19:59 GMT on Sunday.
The failure to reach any agreement in the rare Sunday sitting of the Senate was the result of the actions of Rand Paul.
A libertarian, Mr Paul used a Senate technical procedure to block an extension of the Patriot Act, arguing that data collection is illegal and unconstitutional.
Two weeks ago, he led a filibuster – using extended debates to delay or block the passing of legislation – to stop the quick passage of the Freedom Act.