President Barack Obama answers questions during a press conference in the East Room of the White House August 9, 2013 in Washington, DC. Obama answered questions on national security issues and related matters during the press conferece. (Photo by Win McNamee/Getty Images)

When President Obama was first asked about controversial National Security agencies programs two months ago, he struck a defiant tone, rejecting the notion that what Edward Snowden had revealed constituted any kind of controversy.

“Congress is continually briefed on how these (programs) are conducted. There are a whole range of safeguards involved. And federal judges are overseeing the entire program throughout. And we’re also setting up — we’ve also set up an audit process when I came into office to make sure that we’re, after the fact, making absolutely certain that all the safeguards are being properly observed,” he said then.

Now, his tone has changed. Obama still defends these programs as being both necessary for national security and not violating the civil liberties of Americans. But his announcements at a press conference Friday illustrate he was eager to quiet strong  criticism from even liberals and long-time supporters about the collection of phone records of Americans by the NSA.

The president said he would appoint a panel of outside experts to review U.S. intelligence gathering, appoint a “full-time civil liberties and privacy officer” at the NSA, review provisions in the Patriot Act that authorize the collection of phone records and create a system in which the government’s position is challenged by an adversary in cases that go to the Foreign Intelligence Surveillance Court.

Obama did not apologize for the NSA programs. But he also acknowledged the need for greater public debate and oversight of them, as his critics have repeatedly called for.

“We’re going to resolve our differences in the United States, through vigorous public debate, guided by our Constitution, with reverence for our history as a nation of laws and with respect for the facts,” he said.

Like a speech earlier this year in which President Obama laid out a detailed legal case for his use of drones to kill terrorists abroad, Obama’s illustrated the tensions of the one-time liberal constitutional law professor facing criticisms he was taking actions as president outside of his legal authority.  A majority of Democrats in Congress last month joined a bloc of Republicans who pushed for a provision that would have required the NSA to stop the phone collection program. The provision narrowly failed, but showed the depth of bi-partisan concern with the program.

“It’s not enough for me, as president, to have confidence in these programs. The American people need to have confidence in them as well,” Obama said.

Obama’s move is likely to shift the politics around the debate over the NSA programs. Until Friday, the president was facing an unusual array of critics, that included people like Kentucky’s Rand Paul who disagree with everything Obama does, but also even Illinois Sen. Richard Durbin, a longtime Obama ally who had encouraged him to run for president. At the same time, a vocal bloc of Republicans was calling on the president to defend the NSA at all costs.

Now, liberals are likely to join Obama’s call for greater public disclosure of these programs, damping criticism the president was taking from his political base. At the same time, already some Republicans are attacking Obama’s decision to introduce greater oversight to the NSA.

“It is difficult to imagine past war leaders such as Franklin Roosevelt or Winston Churchill willingly surrendering signals intelligence tools that are needed to fight our enemies,” said New York Republican Rep. Peter King, a member of the House Intelligence Committee.