Top US intelligence officials have defended the surveillance activities conducted by Washington's National Security Agency (NSA), including spying on its allies.
Director of National Intelligence James Clapper has said US spying on foreign leaders has been a "top tenet" for Washington.
Clapper told the House Intelligence Committee: "As long as I've been in the intelligence business, 50 years, leadership intentions in whatever form that's expressed is kind of a basic tenet of what we are to collect and analyse, It's invaluable to us to know where countries are coming from, what their policies are, how that would impact us across a whole range of issues."
When pressed whether other nations spy on American authorities, Clapped replied "absolutely".
NSA chief General Keith Alexander, who testified before the committee, also denied the US has been snooping on European citizens and said the claims to this effect made by Edward Snowden are "completely false".
Alexander said: "To be perfectly clear, this is not information that we collected on European citizens. It represents information that we, and our NATO allies, have collected in defence of our countries and in support of military operations."
The NSA head said much of the information on European nationals was collected by the intelligence agencies of the respective governments and later shared with the US.
It was earlier reported that the US spied on millions of European citizens and high-profile politicians, sparking condemnation from France, Germany and Spain.
Alexander told the committee: "It is much more important for this country that we defend this nation and take the beatings than it is to give up a programme that would result in this nation being attacked."
The remarks from intelligence chiefs came even as many US lawmakers are lobbying for serious changes to America's spying policies.
The hearing is also seen as a platform for discussions on bringing changes to the US's 35-year-old Foreign Intelligence Surveillance Act, popularly known as Fisa.
The White House has admitted the Obama administration is mulling reforms to the US spy programme.
White House spokesperson Jay Carney told reporters: "In general the president is supportive of the idea that we need to make some reforms, [in order to] increase the confidence that the American people have in these programmes, and to perhaps provide greater oversight and greater transparency as well as more constraints on the authorities that exist."