All arrangements have been concluded for some German top intelligence chiefs who would be travelling to Washington to pursue an investigation into allegations the US spied on the German leader Angela Merkel.

According to CEOAFRICA.com findings, the move would enable them to hold talks with the US officials and the National Security Agency.

It was revealed that the phone of Mrs Merkel was bugged, while there are claims that the NSA has monitored millions of telephone calls by both German and French citizens.

Aside from Germany, European countries like Spain, France and Italy have raised questions about reports of spying by US government in their countries.

US state department spokesperson Jen Psaki acknowledged that the revelations - most of them sourced to former US intelligence worker Edward Snowden - have "posed a moment of tension with some of our allies".

"We are having discussions with those allies, those will continue, as is evidenced by the German delegation that will be coming here in the coming weeks," she said.