Dozens of companies, non-profits and trade organizations including Apple Inc, Google Inc and Facebook Inc sent a letter on Thursday pushing the Obama administration and Congress for more disclosures on the government's national security-related requests for user data.

General Keith Alexander, director of the National Security Agency, suggested he was open to the idea but that officials were trying to determine a way to disclose that information without jeopardizing FBI investigations.

"We just want to make sure we do it right, that we don't impact anything ongoing with the FBI. I think that's the reasonable approach," Alexander told the Aspen Security Forum in Colorado, when asked about the letter.

Together with LinkedIn Corp, Yahoo! Inc, Microsoft Corp, Twitter and many others, the companies asked for more transparency of secret data gathering in the letter addressed to Alexander as well as President Barack Obama, Attorney General Eric Holder and national security leaders in Congress.

Tech companies have been scrambling to assert their independence after documents leaked last month by former US security contractor Edward Snowden raised questions about how much data on their clients they handed over to the government to aid its surveillance efforts.

The leaks have renewed a public debate over the balance between national security and privacy, and have put tech companies in an awkward position, especially because many have been assailed for their own commercial use of customer data.

Some companies, including Facebook and Apple, struck an agreement in June with the government to release some information about the number of surveillance requests they receive. But they were limited to disclosing aggregate government requests for data without showing the split between surveillance and criminal requests, and only for a six-month period.

In Thursday's letter, they asked to be allowed to regularly report statistics on the number and scope of user data requests done under specific national security authorities and the number of individuals, accounts or devices affected by those requests.