U.S. officials are alerting some foreign intelligence services that documents detailing their secret cooperation with the United States have been obtained by former National Security Agency contractor Edward Snowden, according to government officials. Snowden, U.S. officials said, took tens of thousands of documents containing sensitive material about collection programs against adversaries such as Iran, Russia and China, operations that in some cases involve countries not publicly allied with the United States. The process of informing officials in capital after capital about the risk of disclosure they face has been painful and delicate. In some cases, one part of the cooperating government may know about the collaboration while others — such as the foreign ministry — may not, the officials said. The documents, if disclosed, could compromise operations, officials said.The duty of informing these other intelligence services, according to the Post, has fallen to the the Office of the Director of National Intelligence. This news comes as the administration is on the defensive about allegations that the NSA monitored the cell phone of German chancellor Angela Merkel. President Obama spoke with Merkel on Wednesday, where he "assured the chancellor that the United States is not monitoring and will not monitor the communications of the chancellor," according to Politico.