The Obama administration is pushing to amend existing privacy law in a way that critics argue would allow the government access to internet browsing histories and other metadata -- without needing a warrant.

An amendment to the Electronic Communications Privacy Act (ECPA), set to be considered by the Judiciary Committee on Thursday, will allow the FBI to subpoena records associated with Americans' online communications -- so called electronic communications transactional records -- with the use of national security letters, which don't require court approval.

That would allow federal agents to access phone logs, email records, cell-site data used to pinpoint locations, as well as accessing a list of visited websites.

Sen. John Cornyn (R-TX), who introduced the amendment, said the change was necessary to prevent "needlessly hamstringing our counterintelligence and counterterrorism efforts."

Under existing law, national security letters can get access to all kinds of metadata -- but not contents of calls, emails, and other messages. But they don't permit the collection of website addresses, or internet search queries. (That said, the FBI is said to have secret legal interpretations allowing it to collect web histories in some cases.)

That's a problem for FBI director James Comey, who called the omission of the provision in the original law a "typo," arguing that it "affects our work in a very big and practical way," he told members of the Senate Intelligence Committee in February.

Or as the EFF staff attorney Andrew Crocker explained in a blog post, "the FBI thinks it was already entitled to get these records using [national security letters], and Congress simply messed up when it drafted the law."

But the Justice Dept.'s Office of Legal Counsel found in 2008 that the FBI was wrong. That's why the FBI is making the push for a change in the law -- making it the second second such push in a decade.

Those privacy advocates are also back, and they brought with them key allies from the tech industry -- including Apple, Facebook, Google, Microsoft, and Yahoo, -- which were among dozens of signatures on an open letter to the Obama administration asking the government to drop the attempt.

"We would oppose any version of these bills that included such a proposal expanding the government's ability to access private data without a court order," says the open letter, dated Monday.

"The civil liberties and human rights concerns associated with such an expansion are compounded by the government's history of abusing NSL authorities," it adds.

But national security letters will still face some level of scrutiny, thanks to a provision in the Freedom Act, which replaced parts of the controversial Patriot Act, which allow secret demands for customer data to be periodically reviewed.

Leading senior senators have rejected the amendment, and will instead push for ECPA reforms, dubbed the Email Privacy Act, which was passed by the House earlier this year.

We reached out to the FBI for comment.