President Obama should not bend to pressure from U.S. law enforcement and intelligence communities and force technology companies to install surveillance “backdoors” that renders encryption impossible. That's the message of a new letter to the president from Apple, Google and a number of leading tech experts who warn that if the FBI can monitor a phone through a backdoor, so can hackers and foreign governments.

“Strong encryption is the cornerstone of the modern information economy's security,” says the letter, obtained by the Washington Post before it was to be sent Tuesday. The 140 companies, cryptologists and “civil society groups” urge Obama to “fully support and not undermine efforts to create encryption standards” and not “in any way subvert, undermine, weaken or make vulnerable” popular communication tools like the iPhone or Android.

The U.S. Department of Justice and FBI have said they, like Apple and Google, support encryption, though they'd still like to monitor Americans' data for law enforcement purposes. But security experts have said that all backdoors -- shorthand for technology that exploits a phone or computer's operating system for surveillance purposes -- are created equal. FBI Director James Comey criticized Google and Apple last year for turning on encryption on their new products by default, meaning neither company has the capability to unlock their customers' products.

The full list of signatories has yet to be revealed, but the Post report also notes that three of the five men Obama appointed to the independent review board following Edward Snowden's disclosures about widespread, indiscriminate surveillance by the National Security Agency have added their names.

“If I actually thought there was a way to build a U.S. government-only backdoor, then I might be persuaded,” Paul Rosenzweig, a former senior policy official at the Department of Homeland Security under President Bush, told the Post. “But that's just not a reality.”