(CNN) -- European lawmakers took their push for answers on U.S. surveillance programs to the White House on Wednesday, meeting with Deputy National Security Adviser Lisa Monaco and other National Security Council staffers.
This is "an extremely important issue of trust between the European Union and the United States," said Claude Moraes, head of the nine-member European Union delegation tasked with investigating disclosures of American spying on European leaders and citizens.
"We want to get to the truth of these allegations" and rebuild a relationship of trust, he added.
Members of the European Parliament's civil liberties committee have been in Washington since Monday, and have also held discussions with officials from the State Department, Congress and intelligence agencies.
Germany sent a separate delegation to the White House after revelations the U.S. government monitored Chancellor Angela Merkel's cell phone.
The news sparked an indignant response from the European powerhouse, a key U.S. ally. Merkel pronounced German confidence in the United States "shaken."
Moraes dismissed a defense offered by a number of U.S. officials -- namely, that all countries spy on each other.
"This old chestnut of 'spying has always happened' just can't stand," he said. "Spying has always existed, but friend-on-friend spying is not something that is easily tolerable."
But another member of the delegation, Britain's Timothy Kirkhope, acknowledged that the United States and EU member states need to strike "a difficult balance" between security and privacy concerns.
"I have trust in the United States and its democracy," Kirkhope told reporters. "It's not for me to tell you or anyone in the United States what to do."
Revelations of U.S. spying involving allied leaders and citizens have sparked calls for the United States to roll back its surveillance programs and triggered threats of repercussions.
On Wednesday, French Foreign Ministry spokesman Romain Nadal said authorities there have demanded an explanation from the United States about surveillance activities.
In Spain, Prime Minister Mariano Rajoy said the nation's intelligence chief will brief lawmakers about what Spain knows about U.S. activities in a closed-door session in Madrid.
Last week, the European Parliament passed a nonbinding resolution calling for the end to a treaty with the United States allowing for the exchange of some banking data meant to help track terrorist financing.
Without providing details, the European Union delegation described its talks as an opportunity to explore "possible legal remedies for EU citizens" affected by U.S. surveillance.
The meeting between the Germans and the White House follows an agreement between Merkel and President Barack Obama to "intensify further the cooperation between U.S. and German intelligence services," NSC spokeswoman Caitlin Hayden said.
Meanwhile, U.S. intelligence leaders began to publicly push back Tuesday against the European complaints.
National Security Agency chief Gen. Keith Alexander denied Tuesday that the United States had collected telephone and e-mail records directly from European citizens, calling reports based on leaks by former NSA contractor Edward Snowden "completely false."
Testifying Tuesday alongside Alexander before the House Intelligence Committee, Director of National Intelligence James Clapper told lawmakers that covert spying among nations was a "fundamental given."
Despite such defenses, the White House is reviewing U.S. intelligence gathering operations.
"We need to look at and make sure that we are not just gathering intelligence because we can, but we're gathering it because we need it," White House spokesman Jay Carney told reporters Tuesday, echoing similar comments earlier by Obama in an interview with Fusion TV.
The review should be completed by the end of the year, Carney said.