Rarely has modern politics produced a leader with the eloquence of Barack Obama, when he sets out to define a pressing crisis.

But the US president's critics, and even some supporters, sometimes question if the zeal of his rhetoric will be matched with action.

That contradiction underscored Obama's long-awaited speech on reining in the National Security Agency (NSA) on Friday, which was in many ways a portrait of his presidency in miniature.

At the end, despite actions Obama has taken or pledged to take, it was still uncertain whether his reforms -- including curtailing but not ending bulk phone data collection -- were symbolic or significant.

"Although we're heartened by many of the positive steps that the President outlined today, many key questions and reforms were left unaddressed," said Sascha Meinrath, director of the New America Foundation's Open Technology Institute.

"Many controversies (were) punted to Congress or to other government officials."

By calling on lawmakers and key players like the NSA and the Justice Department to join the debate, Obama ensured prolonged wrangling over reform in Washington's polarized political echo chamber.

It remains unclear how much muscle he can or will deploy to drive reform into law.

Friday's speech, like many in the past, revealed Obama's own political self image as a reasonable, unifying figure, is intact, despite bitter battles with Republicans and claims he is the most divisive US leader in decades.

Obama portrayed himself as a pragmatist navigating his nation through thorny territory to align the structures of the war on terror to US founding values.

He followed a familiar, methodical formula, in a professorial tone and patching in a lawyerly airing and dismissal of possible counter arguments.

Obama, who built a career on rhetoric, often frames set piece speeches with a parable of American history.

On Friday, before discussing the work of US spies dedicated to giving advance warning of terrorist attacks, he cited Paul Revere, who warned of approaching enemy British soldiers during the Revolutionary War.

Scene set, he turned to the question of the hour: what should America do following massive disclosures of US snooping by fugitive spy Edward Snowden?

He sketched the context of the paranoid days after September 11, 2001, when US spies were under huge pressure to stop the next attack.

"Yet, in our rush to respond to very real and novel threats, the risks of government overreach -- the possibility that we lose some of our core liberties in pursuit of security -- became more pronounced," he said.

His answer to the problem was classic Obama.

Caught between intelligence agencies on one side and civil liberties groups on the other, he suggested a pragmatic, middle course.

"Those who are troubled by our existing programs are not interested in a repeat of 9/11, and those who defend these programs are not dismissive of civil liberties," he said.

Obama intends to curtail certain NSA powers, but will not end the bulk phone data programs entirely.

In a similar vein, Obama announced a military surge to Afghanistan in 2009, but at the same time stipulated a date in 2011 for troops to come home.

Even his vaunted health care reform represented a compromise between the hopes of liberal supporters and the kind of plan it was possible -- just -- to pass.

Reaction to Obama's speech on Friday betrayed uncertainty as to how far reform would go.

"While these procedural reforms to the bulk collection of metadata are welcome, they fall far short of ending the program as the President claimed,” said Brett Solomon, Executive Director of Access a grass roots digital rights organization.

"Real reform is needed and it's needed now."

Typically, Obama used his speech to offer a facsimile of counter arguments to his thesis, and then dismissed them.

"We cannot unilaterally disarm our intelligence agencies," Obama said to those who want bulk collection to end.

To those who want no reform, he said: "our system of government is built on the premise that our liberty cannot depend on the good intentions of those in power; it depends upon the law to constrain those in power."

In another familiar tactic, Obama also targeted multiple constituencies.

He praised US spies, the sincerity of civil liberties groups, chided US allies for moaning about American espionage and even signaled to "Mr Snowden" that he could expect no clemency.

And he managed a shot at Russia and China, noting they would not allow debate on spying, before ending in a typical call to common national purpose and values.

"Together, let us chart a way forward that secures the life of our nation, while preserving the liberties that make our nation worth fighting for."