President Barack Obama has pledged greater transparency in overhauling Washington's controversial surveillance programmes.

During a White House press conference, the US president promised "appropriate reforms" in a bid to build public trust. His comments follow the revelations made by whistleblower Edward Snowden.

The move is tantamount to Obama's first admission of defeat in the ongoing fallout of leaks surrounding the NSA's covert spy programme. The Obama administration, however, continues to defend the programmes despite widespread criticism.

"Given the history of abuse by governments, it is right to ask questions about surveillance, particularly as technology is reshaping every aspect of our lives," Obama said.

He admitted the US "can and must be more transparent" with regard to monitoring and tracking telephone and email conversations. He also confessed that disclosure of the NSA's clandestine activities have damaged Washington's reputation, both within the country and outside.

He continued: "It's not enough for me as president to have confidence in these programmes. The American people need to have confidence as well."

The president also vowed to work with Congress in reforming the Patriot Act to offer greater oversight and transparency. Section 215 of the act allows the NSA to gather information from millions of civilians without providing a warrant.

He also promised to work with legislators in refurbishing the foreign intelligence surveillance (Fisa) court, the legal framework which authorises the NSA to carry out secret programmes.

Obama also took the opportunity to censure Russia's move to grant asylum to Snowden. He said Moscow has been exhibiting more anti-US rhetoric since Vladimir Putin took over as president.

"I've encouraged Mr Putin to think forward as opposed to backwards on those issues, with mixed success," said Obama, adding Snowden was not the only factor dampening US-Russia relations.

Obama earlier cancelled a scheduled summit with his Russian counterpart in Moscow, as a direct snub. And when asked about Snowden, Obama said: "I don't think Mr Snowden was a patriot."