WASHINGTON - Secretary of State John Kerry's remark that some National Security Agency surveillance "reached too far" was the first time a high-ranking Obama administration official acknowledged that U.S. snooping abroad might be seen as overzealous.

After launching into a vigorous defense of surveillance as an effective counterterror tool, Kerry acknowledged to a video-conference on open government in London that "in some cases, I acknowledge to you, as has the president, that some of these actions have reached too far, and we are going to make sure that does not happen in the future."

"There is no question that the president and I and others in government have actually learned of some things that had been happening, in many ways, on an automatic pilot because the technology is there," Kerry said, responding to a question about transparency in governments.

Kerry was responding to questions from European allies about reports in the past two weeks that the National Security Agency had collected data on tens of millions of Europe-based phone calls and had monitored the cell phones of 35 world leaders, including that of German Chancellor Angela Merkel.

The State Department said Friday his remarks were in sync with what President Barack Obama has already said on the controversial spying practices. But Obama has said the administration was conducting a review of surveillance practices and said that if the practices went too far they would be halted.

Kerry first joked with British Foreign Secretary William Hague, whom he said should also answer the question about surveillance because otherwise, would it mean that Britain did not do its own surveillance abroad? The joke was a subtle jab at the U.S. position that allies spy on each other routinely.

Kerry said in the wake of 9/11, the United States and other countries realized they were dealing with a new brand of extremism where people were willing to blow themselves up, even if it meant civilians would be killed.

"There are countless examples of this," Kerry said, citing the Sept. 21 al-Qaida-affiliated al-Shabab attack on the Westgate Mall in Nairobi, Kenya, which killed at least 67 people.

"So what if you were able to intercept that and stop it before it happens?" Kerry asked. "We have actually prevented airplanes from going down, buildings from being blown up and people from being assassinated because we've been able to learn ahead of time of the plans."

Asked if Kerry's comments were off-the-cuff or part of a formal administration response to irritated allies, State Department spokeswoman Jen Psaki said Kerry was reiterating the same comments administration officials have been conveying all week. However, Obama has said that just because the technology exists to conduct certain kinds of surveillance, it doesn't mean the U.S. should use it.

"I think that we wouldn't be having a review if we didn't think we should look at these programs. That's exactly what we're doing," Psaki said. She said Kerry was conveying "what we all feel, which is that this warrants taking a close look at, evaluating our appropriate posture as it comes to heads of state, how we coordinate with our allies, addressing concerns expressed by our allies, working with them, taking into account their input as well and seeing if we can strengthen our cooperation moving forward."

In an interview on Monday with Fusion, Obama said intelligence capabilities have continued to develop and expand in recent years.

"That's why I'm initiating now a review to make sure that what they're able to do doesn't necessarily mean what they should be doing," Obama said.

"Internationally, there are less constraints on how our intelligence teams operate, but what I've said - and I said actually even before the Snowden leaks - is that it's important for us to make sure that, as technology develops and expands, and the capacity for intelligence-gathering becomes a lot greater that we make sure that we're doing things in the right way and that are reflective of our values," Obama said.