WASHINGTON -- U.S. President Barack Obama's orders to change some American surveillance practices puts the burden on Congress to finally deal with a national security controversy that has spooked Americans and outraged foreign allies.

But his proposed changes already have broad political support and avoid major action on one National Security Agency spy system that has far more reach.

Obama said very little Friday to assuage fears that the NSA will continue to sweep up billions of phone, email and text messages from across the globe.

In a speech at the Justice Department, Obama admitted that he has been torn between how to protect privacy rights and how to protect the U.S. from terror attacks -- what officials have called the main purpose of the spy programs.

"The challenge is getting the details right, and that is not simple," Obama said.

His speech had been anticipated since former NSA analyst Edward Snowden made off with an estimated 1.7 million documents related to surveillance and other NSA operations and gave them to several journalists around the world. The revelations in the documents -- which brought upon Snowden criminal charges that he is hiding from in Russia -- sparked a public debate about whether Americans wanted to give up some privacy in exchange for intelligence-gathering on terror suspects.

Privacy advocates and some lawmakers had sharp criticism for the speech's scant attention to an NSA program that intercepts billions of overseas Internet messages and phone conversations from foreigners each day.

The program, authorized under Section 702 of the Foreign Intelligence Surveillance Act, allows the U.S. government to read or listen to the messages and phone calls as long as they do not target American citizens living overseas. It is so massive that the NSA has built a sophisticated recording system to store and review the daily flood of messages and give analysts time to sort through a barrage of real-time content.

Obama said he would seek new restrictions on the government's ability to collect or use the overseas messages that accidentally included messages or phone calls from Americans. But he did not spell out how or by when.

Nor did Obama specify any sweeping changes to the so-called 702 program to protect foreigners' privacy, although he did broadly promise to order "the unprecedented step of extending certain protections that we have for the American people to people overseas." He said that would include limiting the time that the U.S. holds the foreign information it collects -- which officials have said can vary -- while also restricting its use.

Given the mass of the foreign communications surveillance, the reforms offered Friday extended just a "sliver" of respite from fears of U.S. spying, said Matt Simons, director of social and economic justice at Chicago-based software company ThoughtWorks.

"There was a clear attempt to narrow down what we're talking about to the easiest, lowest hanging fruit," said Simons, whose company is among a number of U.S. tech firms demanding broad reforms to prevent their clients from defecting to foreign firms that might offer more protections. Many of the Internet messages collected by the NSA were from accounts on U.S.-based providers, including Microsoft, Yahoo, Google and Facebook.

Mark Jaycox, legislative analyst at the Electronic Frontier Foundation in San Francisco, predicted that the foreign surveillance under Section 702 will be Congress' next target after the government stops collecting and storing Americans' phone records. The EFF is a civil liberties program that is suing the NSA to reveal more information about the programs.

Three Democrats on the Senate Intelligence Committee indicated that changes to the Section 702 spy program would be next on their agenda.

Sens. Ron Wyden of Oregon, Mark Udall of Colorado and Martin Heinrich of New Mexico said in a joint statement that foreign surveillance needs to ensure that Americans' communications are not inadvertently collected, and that U.S. tech firms and products are not "recklessly" undermined by intelligence-gathering in the name of tracking terrorists.

"Additional surveillance reforms are necessary and we will continue to push for these reforms in the coming weeks and months," the senators said, shortly after Obama finished speaking.

It was clear that Obama's orders, however lacking, makes it nearly impossible for reluctant leaders in Congress to avoid making some changes to the U.S. phone surveillance they have supported for years. Even Obama acknowledged more needs to be done, and largely left it to Congress to work out the details.

Since Snowden's revelations began to emerge last June, the surveillance program that has generated the most furor is the daily collection of hundreds of millions of Americans' telephone records.

The NSA says it does not listen in on the phone calls or read the Internet messages without specific court orders. But intelligence officials do collect specific information about the calls and messages, including how long they lasted, what time they were initiated and the phone numbers of each party, to try to track suspected terrorists' communications.

Obama ordered new limits on the way intelligence officials access phone records from hundreds of millions of Americans -- and moved toward eventually stripping the massive data collection from the government's hands.

The president said his proposals "should give the American people greater confidence that their rights are being protected, even as our intelligence and law enforcement agencies maintain the tools they need to keep us safe."

His promises to end government storage of data on Americans' telephone calls -- and require judicial review to examine the data -- also were met with skepticism from privacy advocates and some lawmakers. They likened the proposal a shell game -- by assigning the collection to a new, as-of-yet undecided entity instead of ending it outright.

Plans to end the sweep of phone records have been building momentum in Congress among both liberal Democrats and conservative Republicans. Congressional leadership and the chairmen of the intelligence committees who for years have signed off on the programs, however, have opposed dramatic changes and, in effect, delayed votes on the reforms. As of Friday, at least 145 support the major reform bill.

Obama's order signals that the phone programs most likely will be overhauled, and lawmakers called his speech a welcome first step.