Snowden, a former US intelligence contractor, provided classified documents with evidence of the alleged spying scandal.
German newspaper Bild am Sonntag newspaper reported Sunday that US President Barack Obama was aware of the alleged monitoring of mobile phone communications of Merkel years ago. But the claim was denied by the US side.
The German government has voiced its anger at possible US intelligence's tapping of Merkel's phone, saying it would be "a serious breach of trust" if confirmed.
