The top US intelligence director told lawmakers on Tuesday that discerning other leaders' intentions had long been a goal for spy agencies both in the US and abroad. James Clapper (pictured right) told the House Intelligence Committee it was crucial to know whether what world leaders say "gels what's actually going on."

"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 analyze," Clapper said.

"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."

Asked if America's allies have carried out espionage against the United States, Clapper said: "Absolutely."

The nation's spy operations have come under heavy scrutiny in recent days following allegations that the National Security Agency monitored the communications of up to 35 world leaders, including German Chancellor Angela Merkel.

The revelation, based on documents leaked by former NSA analyst Edward Snowden, was met with anger in Germany and across Europe, although the United States has so far avoided confirming whether Merkel was indeed targeted. The extent of US president Barack Obama's knowledge of the policy also remains unclear.

When questioning Clapper, the chairman of the House Intelligence Committee, Mike Rogers, did not refer specifically to the latest reports.

Rogers said the "best way" to determine a foreign leader's plans was "to somehow either get close to a foreign leader or actually get communications of the foreign leader," and asked Clapper: "Would that be accurate?"

The spy chief replied: "Yes, it would."

'NATO allies assisted NSA operations'

Also testifying before the committee was NSA director, Gen. Keith Alexander (pictured left), who asserted that reports the NSA had also collected data on tens of millions of phone calls across Europe were "completely false."

Alexander told the committee some of the data referenced in the documents had been collected not just by the NSA, but also by foreign allies.

"This is not information that we collected on European citizens. It represents information that we and our NATO allies have collected in defense of our countries and in support of military operations."

Newspapers in France, Spain and Italy reported the allegations, again based on documents leaked by Snowden, to widespread criticism. Spain's prosecutors office announced Tuesday that it had opened a preliminary inquiry to determine whether a crime was committed by NSA surveillance.

Tuesday's hearing took place as multiple reviews of NSA programs are being launched by the White House and Congress. Hours earlier, the White House announced that Obama had ordered a full review of the program and was considering changes.

Moreover, in a rare bipartisan agreement on Tuesday, Senate Majority Leader Harry Reid, a Democrat, and House Speaker John Boehner, a Republican, both said it was time for a thorough review of NSA programs.

ccp/ch (AFP, Reuters, AP)