The world's largest technology companies have a message for U.S. President Obama: don't mess with smartphones.

Two technology organizations representing Apple, Facebook, Google, Twitter and other notable businesses sent a letter to Obama on Tuesday urging his administration not to pursue any policies that would weaken existing encryption measures for fear of undermining the security of users.

"We are opposed to any policy actions or measures that would undermine encryption as an available and effective tool," the Information Technology Industry Council and the Software & Information Industry Association wrote in the joint letter.

"Doing so would compromise the security of ICT [information and communications technology] products and services, rendering them more vulnerable to attacks and would erode consumers’ trust in the products and services they rely on for protecting their information."

In recent months, Obama has suggested that there may be a need for a workaround to strong encryption on personal devices in certain instances when law enforcement may need access to smartphones or applications to investigate suspected terrorists.

“If we find evidence of a terrorist plot… and despite having a phone number, despite having a social media address or email address, we can’t penetrate that, that’s a problem,” Obama said in January. He then noted that technology companies should help find a solution, calling these businesses "patriots."

Clearly Silicon Valley has other ideas.

"Mandating the weakening of encryption or encryption 'work-arounds' is not the way to address this need," the organizations wrote in the letter. "We are committed to finding pathways forward that preserve security, privacy, and innovation... We look forward to continuing this discussion with your administration."

Silicon Valley and the Obama administration once enjoyed a historic bromance, but the relationship became more strained in the wake of whistleblower Edward Snowden's revealing documents that alleged the National Security Agency mined data through companies like Google, Facebook and Microsoft as part of a secret surveillance program.

Tech executives were not shy about their frustrations. Some, like Facebook CEO Mark Zuckerberg, warned that the U.S. government "need to be much more transparent about what they're doing" or else "people will believe the worst." Others like Yahoo and Cisco said the revelations could hurt their reputations and perhaps even their sales abroad.

The latter fear may prove to be true, at least according to a study released this week from the Information Technology and Innovation Foundation. The report estimates that fallout in the foreign markets from the surveillance issue will cost U.S. technology companies more than $35 billion through next year.

"It has become clear that the U.S. tech industry as a whole, not just the cloud computing sector, has under-performed as a result of the Snowden revelations," the report says.

No wonder the technology industry doesn't want to play ball with Obama's plan on encryption.