Media playback is unsupported on your device Media caption A summary of US spying allegations brought about by Edward Snowden's leak of classified documents

The White House and top US lawmakers have rejected clemency for the fugitive intelligence analyst Edward Snowden.

"Mr Snowden violated US law. He should return to the US and face justice," said White House adviser Dan Pfeiffer.

Mr Snowden asked for international help to persuade the US to drop spying charges against him in a letter given to a German politician.

Mr Snowden, 30, fled to Russia in June after leaking details of far-reaching US telephone and internet espionage.

He was granted temporary asylum, allowing him to live in Russia until July 2014.

In a surprise move last week, a German Green MP met Mr Snowden in Moscow and revealed the former intelligence contractor's readiness to brief the German government on National Security Agency's (NSA) spying.

German news magazine Der Spiegel on Sunday published an open letter that it said was by Mr Snowden, in which he says the impact of his leaks have been positive.

"Instead of causing damage, the usefulness of the new public knowledge for society is now clear because reforms to politics, supervision and laws are being suggested," it said.

"Citizens have to fight against the suppression of information about affairs of essential importance for the public. Those who speak the truth are not committing a crime."

Mr Snowden also set out his position in a letter, which Hans-Christian Stroebele showed to reporters at a news conference in Berlin on Friday.

"Speaking the truth is not a crime," Mr Snowden wrote. He claimed that the US government was persecuting him by charging him with espionage.

On Sunday, the White House said that no offers for clemency were being discussed.

This view was echoed by the Republican Congressman Mike Rogers and Democratic senator Dianne Feinstein.

She said that if Mr Snowden had been a true whistleblower, he could have reported privately to her committee, but had chosen not to.

"We would have seen him and we would have looked at that information. That didn't happen, and now he's done this enormous disservice to our country," Senator Feinstein said in an interview on CBS television.

"I think the answer is no clemency," she said.

The scale of the alleged US espionage has provoked international concern and calls for tighter supervision.

Reports that the US bugged German Chancellor Angela Merkel's mobile phone for years have caused a diplomatic rift.

The head of US intelligence has defended the monitoring of foreign leaders as a key goal of operations but the US is facing growing anger over reports it spied on its allies abroad.

It has also been reported that the NSA monitored French diplomats in Washington and at the UN, and that it conducted surveillance on millions of French and Spanish telephone calls, among other operations against US allies.

US Secretary of State John Kerry said last week that in some cases, US spying had gone too far.

He said he would work with President Barack Obama to prevent further inappropriate actions by the NSA.