British Foreign Secretary William Hague, speaking at the Ronald Reagan Presidential Library in Simi Valley, called intelligence-sharing between Britain and the U.S. is "unique and indispensable" at a time of unrest around the globe.
"In both our countries intelligence work takes place within a strong legal framework," Hague said. "We operate under the rule of law and are accountable for it. In some countries secret intelligence is used to control their people—in ours it only exists to protect their freedoms."
"We should always remember that terrorists plan to harm us in secret, criminal networks plan to steal from us in secret, foreign intelligence agencies plot to spy on us in secret and new weapons systems are devised in secret," Hague said.
"We cannot protect the people of our countries without devising some of the response to those threats in secret," he said.
His appearance at the hilltop library comes as the U.S. continues to pursue National Security Agency leaker Edward Snowden. The 30-year-old former NSA contractor gained access to documents that he gave to the Guardian and The Washington Post newspapers to expose what he contends are privacy violations by an authoritarian government.
Earlier this month in London, Hague was forced to deny allegations that the U.K. government had used information provided by the Americans to circumvent British laws.
"We want the British people to have confidence in the work of our intelligence agencies and in their adherence to the law and democratic values," Hague told Parliament.
Snowden, who is charged with violating American espionage laws, touched off a global guessing game over his whereabouts after fleeing Hong Kong over the weekend, frustrating U.S. efforts to bring him to justice.
Russian President Vladimir Putin on Tuesday rejected U.S. pleas to turn him over, saying Snowden is in the transit zone of Sheremetyevo Airport and has not passed through Russian immigration, meaning he technically is not in Russia.
Last week the Guardian, citing British intelligence memos leaked by Snowden, reported that British spies are running an online eavesdropping operation so vast that internal documents say it even outstrips the United States' international Internet surveillance effort.
Hague said citizens can be confident that intelligence-gathering is carried out with "multiple checks and balances" within the laws of the two countries.
In his remarks, Hague said he rejected the notion that western nations face an inevitable decline.
"Some predict gloomily that as emerging powers rise, so we in the West must fall. But our free and open societies are better placed to make the most of changes in the world, to adjust to it and to cope with turbulence," he said.
He also urged more engagement abroad.
"We must build more connections with other countries, adapting our global role, not pulling back from it," he said.
Taking questions from the audience, he dismissed the notion of using a blockade to keep arms from reaching Syria's President Bashar Assad's government in Syria. He also said his country was firmly committed to address global warming and that a scientific consensus warns that failing to do so would have "very serious" consequences.
"Globally, we do have to act on climate change," Hague said.