Leading German intelligence officials are to travel to Washington in the coming weeks to investigate claims that the US has been monitoring Angela Merkel’s phone, reports NBC News.
US government officials said they looked forward to the meeting and confirmed that the spying reports would feature on the agenda.
The Guardian reported earlier this week that, according to documents leaked by whistleblower Edward Snowden, the US was monitoring the phone calls of 35 world leaders.
The UK and US governments are demonising journalists for the "principled" publishing of documents leaked by US whistleblower Edward Snowden to avoid a debate about the impact of their spying disclosures, leading human rights campaigners have said.
A joint statement by Liberty director Shami Chakrabarti and Anthony Romero, the executive director of the American Civil Liberties Union, said: "The Guardian's decision to expose the extent to which our privacy is being violated should be applauded and not condemned."
They said debate in Britain about the impact of the disclosures "is in danger of being lost beneath self-serving spin and scaremongering, with journalists who dare to question the secret state accused of aiding the enemy".
The statement added: "A balance must of course be struck between security and transparency, but that cannot be achieved whilst the intelligence services and their political masters seek to avoid any scrutiny of, or debate about, their actions."
On a trip to Brussels, where his European colleagues were reeling from revelations they may have been spied on by the US, David Cameron was put in an awkward position thanks to Britain's close ties with America.
The Prime Minister initially declined to comment on the matter - before giving a speech defending the UK's intelligence agency.
ITV News' Europe Editor James Mates reports.
David Cameron has backed calls by France and Germany for talks with the United States to resolve the increasingly bitter dispute over spying on its allies by America's National Security Agency.
"The leaders of the European Union issued a good and sensible statement last night about this matter and I agree with that statement," he said.
David Cameron has defended GCHQ amid claims that world leaders' phone calls were monitored, saying British intelligence agencies "keep our people safe".
The Prime Minister told an EU summit: "Every year for the last few years they have helped obstruct major terrorist attacks on our country."
The Prime Minister has launched a strong attack on the US whistleblower Edward Snowden and some newspapers for holding a "lah-di-dah, airy-fairy view" of the intelligence community.
He said that there are people in the world "who want to blow up our families" and that "what Snowden is doing and to an extent what the newspapers are doing" is helping such people to "evade" efforts to stop them.
"That is helping our enemies. Simple" he added.
David Cameron said he would "make no apology" for having and maintaining security services because of the work they do to keep the country safe.
"I will criticise those who make public the work that they do," he added.
The Prime Minister has reiterated his support for the electronic spying agency GCHQ in the wake of claims that 35 world leaders have had their phones spied upon by the US.
“The work they do is vital, they will always have my support and they are properly scrutinised,” he said.
Asked whether David Cameron was comfortable using his mobile after the Angela Merkel US spy revelations, the Prime Minister's spokesman said: "Yes, I haven't seen him use a different one."