Senate Intelligence Committee Chairwoman Dianne Feinstein, D-Calif., on Monday said she was “totally opposed” to the National Security Agency’s surveillance of foreign leaders, including German Chancellor Angela Merkel, and vowed a review of the intelligence programs.

“With respect to NSA collection of intelligence on leaders of U.S. allies—including France, Spain, Mexico and Germany—let me state unequivocally: I am totally opposed,” said Feinstein in a statement.

“Unless the United States is engaged in hostilities against a country or there is an emergency need for this type of surveillance, I do not believe the United States should be collecting phone calls or emails of friendly presidents and prime ministers,” she added.

The latest disclosures from NSA leaker Edward Snowden revealed that the U.S. had monitored the phone calls of dozens of world leaders, including Merkel.

Those revelations sparked anger overseas, with Merkel and Obama speaking by phone about the issue last week. The White House said Obama reassured the German leader that the U.S. is not monitoring her communications now and will not in the future. The White House though has declined to confirm any past monitoring of Merkel’s phone calls.

Feinstein said her committee would launch a probe into the revelations.

“It is abundantly clear that a total review of all intelligence programs is necessary so that members of the Senate Intelligence Committee are fully informed as to what is actually being carried out by the intelligence community,” she said.

“Certain surveillance activities have been in effect for more than a decade,” Feinstein added, claiming that “the Senate Intelligence Committee was not satisfactorily informed.”

“Our oversight needs to be strengthened and increased,” she said.

A report in the Wall Street Journal on Monday said Obama had not learned that NSA electronic surveillance programs had intercepted Merkel’s calls until an internal inquiry conducted this past summer.

Feinstein said that any such surveillance should require the approval of the president, calling it a “big problem” that Obama was not aware sooner of the surveillance, which some reports date back to 2010.

“The White House has informed me that collection on our allies will not continue, which I support. But as far as I’m concerned, Congress needs to know exactly what our intelligence community is doing,” said Feinstein. “To that end, the committee will initiate a major review into all intelligence collection programs.”

National Security Council spokesperson Caitlin Hayden said in a statement that the administration is consulting “regularly” with Feinstein.

“I’m not going to go into the details of those private discussions, nor am I going to comment on assertions made in the Senator’s statement today about U.S. foreign intelligence activities,” she added.

Hayden said the administration’s review of intelligence practices to better balance security and privacy interests was “ongoing.”

“We have already made some decisions through this process and expect to make more as we continue,” she said.

White House press secretary Jay Carney on Monday said the administration was also working to assuage the concerns of allied nations about NSA surveillance through diplomatic channels, but declined to share the substance of those efforts.

He added that the programs were “legal” and had helped protect America’s security and those of its allies.

“The gathering occurs for a purpose,” Carney said.

This story was published at 5:43 p.m. and has been updated.