• Three new co-sponsors for USA Freedom Act • Sensenbrenner: 'Reform cannot be done by presidential fiat'

Critics of National Security Agency surveillance are hoping President Barack Obama's call to stop government collection of telephone data will give fresh momentum to legislation aimed at banning the practice entirely.

On Friday, three new co-sponsors joined the 120 congressmen who have already backed the so-called USA Freedom Act, but their reform bill faces tough competition from rival lawmakers who claim the president's broad support for the NSA favours separate efforts to protect its powers.

Obama forcefully defended the NSA on Friday, in a speech that outlined a series of surveillance reforms but stopped well short of demanding an end to the bulk collection of American phone data, suggesting instead that efforts should be made to find alternatives which do not involve the government holding a database.

But reformers on Capitol Hill are nonetheless in confident mood, believing the president's acknowledgement of the risks of government surveillance will spur more meaningful legislative reform in the coming months.

“Some of his proposals I agree with, others I don’t. But the bottom line is real reform cannot be done by presidential fiat,” said the Republican congressman Jim Sensenbrenner, an author of the Patriot Act who is leading bipartisan reform efforts with the Democratic senator Patrick Leahy.

“[Our] bill would make permanent the good intentions of the president and address some of the omissions in his speech where Americans’ liberties need greater protection. I remain confident that if brought to the floor for a vote, the USA Freedom Act will pass with broad bipartisan report.”

Leading critics within Obama's own party gave a cautious welcome to the president's speech, as they prepared for the pending fight in Congress by seizing on aspects that supported more lasting reform.

“Make no mistake, this is a major milestone in our longstanding efforts to reform the National Security Agency’s bulk collection programme,” said senators Ron Wyden and Mark Udall in a joint statement. “The president has listened to some of the advice of his independent panel of experts and endorsed some of the reforms we have long advocated. The fight to protect liberty and increase security is far from over.”

Senator Leahy added: “In the wake of these announcements, Congress has important tasks ahead. The president has ordered some significant changes, but more are needed.”

But the Leahy/Sensenbrenner bill still faces a significant challenge from lawmakers close to the intelligence community, who say Obama's defence of the NSA supports their position.

The chairs of the Senate and House intelligence committees, Senator Dianne Feinstein and Representative Mike Rogers, issued a joint statement calling on the White House to “send legislation with the president’s proposed changes to Congress so they can be fully debated”.

Though perhaps a tacit acceptance that their earlier bill to strengthen NSA bulk collection may now be dead in the water, Feinstein and Rogers were quick to ally themselves with the president's views.

“President Obama said today that US intelligence programmes have ‘made us more secure’ and that nothing indicates that our intelligence community ‘has sought to violate the law or is cavalier about the civil liberties of their fellow citizens’. We agree and look forward to working with the president to increase confidence in these programmes,” they said.

Sensenbrenner will also have to overcome opposition on the House judiciary committee if he is to move his bill forward, although allies believe sufficient numbers of Republican co-sponsors may pressure the chairman, Bob Goodlatte – once a supporter of reform – to allow mark-up of the bill. Leahy is chair of the Senate judiciary committee, so has more power to call hearings and move the bill forward in the upper chamber.

So far, though, Obama's speech appears to have softened criticism from within his own party, including Democrats in the House, who are keen to take what victories they can in support of future legislation.

“President Obama has taken a courageous first step towards improving oversight of these surveillance programmes, reassuring our foreign allies, and restoring the public’s trust," said John Conyers, of Michigan. “Yet, even if implemented in full, the president’s proposals are not the end of our efforts to reign in excessive government surveillance – they are the first steps.”

The sense that reform-minded Democrats are avoiding alienating the White House ahead of the clash on Capitol Hill was echoed by campaign groups, who urged supporters to continue the battle on multiple fronts.

"Now it's up to the courts, Congress, and the public to ensure that real reform happens, including stopping all bulk surveillance – not just telephone records collection,” said Cindy Cohn, legal director of the Electronic Frontier Foundation.

Republicans in Congress were more blunt in their assessment of the speech. “It's not about who holds it, I don't want them collecting Americans' information,” Senator Rand Paul told CNN.

International campaign groups were also more critical, arguing that there was little substance behind the president’s rhetoric.

“The big-picture takeaway from today's speech is that the right to privacy remains under grave threat both here at home and around the world," said Steven Hawkins, executive director of Amnesty International USA. “President Obama’s surveillance adjustments will be remembered as music on the Titanic unless his administration adopts deeper reforms.”

The American Civil Liberties Union pointed to constitutional challenges in the supreme court as an avenue for more meaningful change.

“The president should end – not mend – the government’s collection and retention of all law-abiding Americans’ data,” said the ACLU's executive director, Anthony Romero.

“When the government collects and stores every American’s phone call data, it is engaging in a textbook example of an ‘unreasonable search’ that violates the constitution. The president’s own review panel recommended that bulk data collection be ended, and the president should accept that recommendation in its entirety.”