The White House indicated on Tuesday that it would support at least some of the congressional efforts to rein in the controversial surveillance practices of the National Security Agency, as political opinion in Washington hardened against the country’s embattled intelligence community.

The administration revealed that an internal government review in the wake of revelations by the whistleblower Edward Snowden had already led to changes in US intelligence-gathering activities – thought to be a ban on eavesdropping on the leaders of friendly governments and a curb on surveillance at the United Nations.

But wider checks on domestic surveillance practices also looked increasingly likely on Tuesday, as bipartisan legislation was introduced in the House of Representatives and Senate and party leaders united in calling for reform.

Even as the White House acknowledged that legislative reform of the NSA was inevitable, senior intelligence officials mounted a uncompromising defence of their current programs. At a congressional hearing, General Keith Alexander, the director of the NSA, forcefully and emotionally rejected calls to curtail his agency’s power. Alexander, who declared he was speaking “from the heart”, said the NSA would prefer to “take the beatings” from the public and in the media “than to give up a program that would result in this nation being attacked”.

At the White House, chief spokesman Jay Carney welcomed the various reform efforts in principle but declined to discuss specific recommendations until the conclusion of a separate White House investigation.

“In general the president is supportive of the idea that we need to make some reforms,” Carney said in response to questions about the new legislation. He said that it was important “to increase the confidence that the American people have in these programmes, and to perhaps provide greater oversight and greater transparency as well as more constraints on the authorities that exist”.

Facebook Twitter Pinterest White House press secretary Jay Carney speaks at the daily press briefing in the Brady press briefing room of the White House in Washington, where he took questions on reviewing intelligence gathering of foreign allies. Photograph: Charles Dharapak/AP

Carney also revealed that the White House review would concentrate on whether the US acted appropriately in relation to surveillance activities on its allies. The White House has been under intense pressure in recent days since reports emerged that the NSA had targeted the cellphone of the German chancellor, Angela Merkel. “The concerns raised by our allies cause us concern too,” Carney said.

The House speaker John Boehner and Senate majority leader Harry Reid also expressed support for reform on Tuesday. "The NSA situation is one we need to look at," said Reid. "I support the complete review of all of these programs."

On Monday night, President Barack Obama said his administration was conducting a complete review of intelligence activities. Interviewed on television network Fusion, Obama said: "What we've seen over the last several years is their capacities continue to develop and expand, and that's why I'm initiating now a review to make sure that what they're able to do doesn't necessarily mean what they should be doing.”

Senator Dianne Feinstein, chairwoman of the Senate intelligence committee, called for a "total review of all intelligence programs" following the Merkel allegations. In a statement on Monday, the California Democrat said the White House had informed her that "collection on our allies will not continue". Carney would not elaborate on that statement on Tuesday.

Facebook Twitter Pinterest US senator Dianne Feinstein arrives for a markup of the Senate select committee on intelligence on Tuesday. Photograph: Win McNamee/Getty Images

The near unanimity among political leaders left intelligence leaders striking an increasingly lonely defence of the practices at a hearing on Capitol Hill.

At a hearing of the House intelligence committee, Alexander argued that a continued threat of terrorism justified retaining the agency’s post-9/11 powers. At the same hearing, the director of national intelligence James Clapper warned the panel to be mindful of the “risks of overcorrection” in surveillance reform – suggesting that proposed restrictions on bulk surveillance would leave the country in danger of a terrorist attack.

Addressing the growing international row over NSA spying, Alexander forcefully argued that reports of the agency collecting millions of Europeans’ phone calls were “absolutely false”.

But Clapper danced around the central question of how much Obama knew about NSA’s separate surveillance activities on foreign leaders. He said that the intelligence agencies “do only what the policymakers, writ large, have actually asked us to do”. He added that the “level of detail” about how those requirements are implemented rarely rose to the attention of presidents.

Two Democratic representatives, Adam Schiff of California and Jan Schakowski of Illinois, suggested that the House intelligence committee was not informed about the foreign leader spying. Clapper, without confirming that the spying took place, said that “we have by and large complied with the spirit and intent of the law”.

Facebook Twitter Pinterest A protester against the practices of US security agenices sits in the audience as intelligence officials testify at a hearing on Capitol Hill. Photograph: JASON REED/REUTERS

Schiff drew a heated and unexpected rebuke from the committee chairman, Republican Mike Rogers, who called his suggestion “disingenuous”. The committee has access to “mounds of product” from the NSA, Rogers said. Schiff shot back a direct question about whether Rogers in fact knew about the foreign leader spying, which Rogers said he could not answer without confirming – but invited the committee member to view reams of intelligence in private.

There is an increasing sense in Washington that Congress, and perhaps the White House, will impose some form limitation on the NSA’s authorities – a rarity since 9/11. Even Charles "Dutch" Ruppersberger, another staunch NSA ally, signalled he was open to transforming the collection of Americans’ call data.

“Can we move away from bulk collection and toward a system like the one used in the criminal prosecution system, in which the government subpoenas individual call data records,” Ruppersberger told the House committee hearing.