Barack Obama has raised for the first time the prospect of new legislation to limit the powers of the NSA, the US spy agency caught up in controversy over the sweep of its surveillance operations.

Answering a question at a joint press conference with Swedish prime minister Frederik Reinfeldt on Wednesday, Obama said there were "legitimate questions" about the NSA. He said existing laws may not be sufficient to deal with advances in technology that have allowed the NSA to gather much more data than before.

There have been calls for new legislation from members of Congress to limit the powers of the NSA, but this is the first time that Obama has hinted he might back such a move. Until now, Obama has only proposed limited changes and is awaiting recommendations from a review body he set up.

The president's language was more sympathetic towards the privacy camp than it has been over the past few months. Just because the US intelligence agencies could do something did not meant it should, Obama said, particularly if the US is being too intrusive in looking into the behaviour of other governments.

Technological changes meant the "risks of abuse are greater than they have been in the past", he said.

Obama, visiting Stockholm on his way to St Petersburg for the G20 summit, held a joint press conference with Reinfeldt that was dominated by the Syria crisis. But the first question was on the NSA from a Swedish reporter, who asked about the extent to which it had stirred up an angry reaction, including in Sweden, and the impact it is having on US relations round the world.

"This is a question I have received in previous visits to Europe since the stories broke in the Guardian; [a question] I suspect I will continue to get as I travel through round the world for quite some time," Obama said.

Defending the NSA, Obama said that the US, like other countries, had an intelligence operation aimed at improving its understanding of what is happening round the world. Since 9/11, he added, much energy had been focused on counter-terrorism.

"What I can say with confidence is that when it comes to our domestic operations, the concerns that people have back home … we do not surveil the American people or persons within the United States. There are a lot of checks and balances in place designed to avoid a surveillance state," Obama said.

"There have been times where the procedures, because these are human endeavours, have not worked the way they should and we had to tighten them up. And I think there are legitimate questions that have been raised about the fact that as technology advances and capabilities grow, it may be that the laws that are currently in place are not sufficient to guard against the dangers of us being able to track so much."

Some members of Congress are pressing for changes to the Patriot Act to end the NSA's power to scoop up the phone records of millions of Americans.

Obama and other US politicians have caused upset with repeated statements that the NSA does not read the emails of Americans or listen in on their phone calls – and that the surveillance applies only to non-Americans.

Addressing this, Obama said: "Now when it comes to intelligence-gathering internationally, our focus is on counter-terrorism, weapons of mass destruction, cybersecurity – core national security interests of the United States. But what is true is that the United States has enormous capabilities when it comes to intelligence."

He added: "One way to think about it is: in the same way that our military capabilities are significantly greater than many other countries, the same is true for our intelligence capabilities. So even though we may have the same goals, our means are significantly greater.

"And I can give assurances to the public in Europe and around the world that we're not going around snooping at people's emails or listening to their phone calls. What we try to do is to target very specifically areas of concern."

Obama was careful to speak only about content and avoided the issue of metadata – the timing, duration, location and other information about phone calls, emails and other private information being scooped up daily round the world by the NSA.

In spite of his insistence that there was no mass snooping on content, Obama acknowledged the concerns. "What I have said domestically – and what I say to international audiences – is with the changes in technology, with the growth of our capabilities, if our attitude is: 'Because we can do it, we should go ahead and do it,' then we may not be addressing some of the legitimate concerns and dangers that exist when we are talking about intelligence-gathering and surveillance."

Apart from the backlash round the world, Obama is also having to contend with problems in the US over surveillance. He hoped to deflect the issue with an announcement last month of minimal changes such as the creation of a review body but the controversy has refused to die.

The review body he set up was derided by some privacy activists as lacking independent voices. The issue will also be kept in the public eye by congressional hearings, court cases and calls by internet companies – suffering from their association with the NSA – for greater transparency.