US spy agencies are not waging a vast industrial espionage campaign on behalf of American companies as alleged by intelligence leaker Edward Snowden, senior officials say.

The US collects economic intelligence to try to assess the stability of governments and trace the financing of terror groups or dangerous weapons, according to intelligence officials who spoke on condition of anonymity.

The goal of economic intelligence efforts is to support national security interests, and "not to try to help Boeing", said one senior intelligence official on Thursday.

The US intelligence community is arguing its case after a wave of leaks by Snowden that exposed the scale of US electronic spying.

Snowden, the fugitive former intelligence contractor who has leaked a trove of classified documents, has accused the National Security Agency of waging economic espionage and scooping up commercial information regardless of its value to national security.

"If there is information, for example on Siemens, which is in the national interest, but has nothing to do with national security, they will still use this information," Snowden said in a January interview broadcast by German public television ARD.

US officials vehemently rejected Snowden's allegation and point to legal restrictions that ban industrial spying under the 1996 Economic Espionage Act.

Economic intelligence gathering and analysis was an increasingly crucial element to the spy agencies' work, officials said, though it was aimed at trying to predict geopolitical trends and disrupt terrorists.

"We could care less about a bank's balance sheet," said a second official, unless the funds are linked to weapons proliferation or extremist groups.

While industrial snooping is prohibited, officials said the law provides an exemption for the intelligence community to "collect for a valid foreign intelligence purpose" such as countering the proliferation of nuclear or other weapons, enforcing sanctions and tracking terrorist threats.

It would be plausible and justified for the agencies to hone in on a company such as Russian-owned Gazprom - given the current crisis in Ukraine, the official said.

In such a case, the intelligence gathering would be justified based on US national security interests, whether to shape a strategic analysis of Russia or examining sanctions issues, officials suggested.

Some media coverage of Snowden's leaks had implied that the US had spied on Brazil's state-owned Petrobas oil firm to help US oil companies.

The officials did not confirm or discuss why Petrobas may have been a focus for the spy agencies. Documents leaked by Snowden reportedly include a slide that names the oil giant as a target.