A White House-appointed panel has proposed limits on some key National Security Agency surveillance operations.

It has recommended limits on a programme to collect records of billions of telephone calls and new tests before the US spies on foreign leaders.

Among the panel's proposals, made in the wake of revelations by former NSA contractor Edward Snowden, the most contentious may be its recommendation that the agency halt collection of the phone call records, which is known as "metadata".

Instead, it said, those records should be held by telecommunications providers or a private third party.

In a further limitation, the US government would need an order from the Foreign Intelligence Surveillance Court to search the data.

"We don't see the need for the government to be retaining that data," said Richard Clarke, a member of the panel and a former White House counter terrorism advisor.

Across US surveillance programmes more broadly, "we tend to believe there should be further judicial oversight than there has been," Mr Clarke said.

It remains to be seen, however, how many of the panel's 46 recommendations will be accepted by US President Barack Obama and the US Congress.

The panel's five members met Mr Obama at the White House today.

NSA officials have staunchly defended the bulk metadata programme, saying it is essential to "connect the dots" between terrorist plotters overseas and co-conspirators inside the US.