US Senate Intelligence Committee Chairwoman Dianne Feinstein on Monday announced that the panel will initiate "a major review" into all US intelligence programs amid uproar following media disclosures about US spying on world leaders.

Feinstein, one of the defenders of the US intelligence surveillance programs that have been under scrutiny since June, issued a statement following reports that the National Security Agency has conducted surveillance on leaders of foreign countries, including Germany Chancellor Angela Merkel.

In the statement, Feinstein said a total review of all US intelligence programs is necessary so that members of the Senate Intelligence Committee could be fully informed of what the intelligence community is carrying out.

"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 the 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. The president should be required to approve any collection of this sort," she said.

She said that "certain surveillance activities", unlike NSA's collection of phone records under a court order, have been in effect for more than a decade and the Senate Intelligence Committee "was not satisfactorily informed."

Feinstein also said that according to her understanding, President Barack Obama was not aware of the collection of Merkel's communications since 2002. "That is a big problem," she added.

She said the White House has informed her that such collections on US allies will not continue.

The White House spokesman Jay Carney said on Monday Obama has full confidence in NSA Director Keith Alexander and the agency's rank-and-file.

The defense of the NSA comes amid outrage and criticism from American allies in Europe over media reports that US intelligence agencies have monitored the communications of Merkel and tens of millions of phone calls in France and Spain.