Yahoo's security chief Alex Stamos clashed with Adm Mike Rogers, the director of the US National Security Agency

A Yahoo executive has publicly challenged the National Security Agency (NSA) over encryption "backdoors".

Alex Stamos pressed NSA director Adm Mike Rogers on whether the access to encrypted data requested by the US authorities should also be granted to the Russian and Chinese governments.

Adm Rogers insisted an agreement could be reached "within a framework".

The tense exchange came after many top tech figures refused to attend a White House cybersecurity summit this month.

"If we're going to build defects, backdoors or golden master keys for the US government, do you believe we should do so... for the Chinese government, the Russian government, the Saudi Arabian government, the Israeli government, the French government?" asked Mr Stamos, Yahoo's chief information security officer.

After initially dodging the question, Adm Rogers - who took over as director of the NSA last year - respondedhttp://www.bbc.co.uk/news/technology-31604503#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa: "I think that we're lying that this isn't technically feasible.