President Barack Obama recently ordered the National Security Agency to curtail eavesdropping on the United Nations headquarters in New York as part of a review of U.S. electronic surveillance, Reuters said, citing a U.S. official familiar with the decision.

Obama's order is the latest known move by the White House to limit the NSA's vast intelligence collection, in the wake of protests by allies, including German Chancellor Angela Merkel, over U.S. spying on foreign heads of state.

The full extent of U.S. eavesdropping on the United Nations is not publicly known, nor is it clear whether the United States has stopped all monitoring of diplomats assigned to the UN in New York or elsewhere around the world.

"The United States is not conducting electronic surveillance targeting the United Nations headquarters in New York," said a senior Obama administration official, who spoke on condition of anonymity.

The official did not address past surveillance of the world body. Such programs are highly classified, although some details have been leaked by former NSA contractor Edward Snowden.

According to the first official, the president's aides have said in briefings that the White House no longer wanted to conduct certain monitoring of UN targets. The official said that the decision was made within the last few weeks.

The NSA declined to comment on the matter. Spokesmen for UN Secretary General Ban Ki-moon did not respond immediately to a request for comment.

Historically, the United Nations and New York-based diplomatic missions of member states have been targets for aggressive spying by the United States, its allies and adversaries. FBI counter-intelligence squads have long mounted operations to try to identify spies posing as UN diplomats.