How much is the US snooping on Europeans?

President Barack Obama sought Wednesday to reassure Europeans outraged over U.S. surveillance programs that his government isn't sifting through their emails or eavesdropping on their telephone calls. He acknowledged that the programs haven't always worked as intended, saying "we had to tighten them up."

Obama said once-secret U.S. surveillance programs that became public knowledge after a government contractor leaked details about them are meant to improve America's understanding of what is happening around the world. He sought to allay the concerns of Europeans upset by the thought their personal communications may have been swept up in the U.S. government's massive data collection operations.

"I can give assurances to the publics in Europe and around the world that we're not going around snooping at people's emails or listening to their phone calls," Obama said at a news conference with Prime Minister Fredrik Reinfeldt on his first visit as president to Sweden. "What we try to do is to target very specifically areas of concern."

Leaks by former National Security Agency contractor Edward Snowden about U.S. surveillance programs sparked outrage overseas, particularly among Europeans who place a premium on personal privacy and civil liberties and recall life under governments that routinely spied on them. The NSA program was the first question he received from the Swedish press.

Obama said additional changes to the programs may be required because of advances in technology. He said his national security team along with an independent board is reviewing everything to strike the right balance between the government's surveillance needs and civil liberties.

"There may be situations in which we're gathering information just because we can that doesn't help us with our national security, but does raise questions in terms of whether we're tipping over into being too intrusive with respect to the ... the interactions of other governments," Obama said. "We are consulting with the (European Union) in this process; we are consulting with other countries in this process and finding out from them what are their areas of specific concern and trying to align what we do in a way that, I think, alleviates some of the public concerns that people may have."

The joint appearance with Reinfeldt was one of several events packed into Obama's whirlwind, 24-hour visit to the Swedish capital to show a softer side of American diplomacy even as the world's gaze remains fixed anxiously on Syria.

He intends to focus in the Nordic nation on climate change, trade and technology, issues on which there is broad consensus with European allies. The topics are a marked departure from the thornier national security and economic matters he's facing back home.

Obama also paid homage to a Holocaust-era hero whose name is commemorated on street signs from Paris to Tel Aviv.

The president arrived Wednesday morning in Stockholm after an overnight flight from Washington, where lawmakers are debating Obama's request for congressional authorization for a military strike against Syria. On Thursday, Obama was scheduled to meet with foreign leaders at the Group of 20 economic summit in St. Petersburg, Russia.

Greeting Obama at the airport on a mild, sunny morning were Swedish Foreign Minister Carl Bildt and leaders of Reinfeldt's center-right coalition government. Sporadic crowds lined the highway as Obama's motorcade sped from the airport and they thickened in central Stockholm, especially around Obama's waterfront hotel.

Obama's trip marks the first bilateral visit by a sitting U.S. president to the northern European nation. Obama will meet with Reinfeldt and King Carl XVI Gustav and dine with Nordic leaders from Norway, Iceland, Finland and Denmark. He'll also stop at Sweden's premier technical university to call attention to Sweden's goal to phase out fossil fuels by 2050.

The White House hastily arranged the Stockholm visit after Obama, incensed when Russia granted asylum to Snowden, scrapped a planned meeting with Russian President Vladimir Putin in Moscow. The cancellation created a two-day scheduling void when Obama was expecting to be overseas but had nowhere to go. The White House added Sweden to his itinerary.

Administration officials offered little in the way of a specific rationale for the visit, other than to say that the country had extended him a written invitation some time ago. They added that Nordic nations are important partners in development, global security and promotion of democracy.

Many of Obama's global priorities — like energy, global trade and science training — parallel his second-term domestic goals as he seeks to ready the U.S. workforce for a higher-tech economy, increase demand abroad for American products and tackle climate change. But those priorities have at times been overshadowed by the global outrage over the massive U.S. surveillance programs revealed by Snowden and by Obama's efforts to persuade nations to take a tougher tack against Syria.

A sobering moment was expected Wednesday afternoon when he honors the late Swedish diplomat Raoul Wallenberg, credited for saving at least 20,000 Jews during World War II before being arrested by Soviet forces in 1945 and then mysteriously disappearing. Wallenberg's family planned to present a letter to Obama asking for help in pressing Russia to shed light on Wallenberg's fate.

Amid tight security, protesters gathered in the streets of Stockholm, including a small group from Amnesty International that demonstrated outside the royal palace to demand that Obama close Guantanamo Bay prison.

Thousands of armed police are deployed on city streets, many roads and parks are closed in the downtown area, concrete barriers and steel fences have sprung up in many locations near where Obama will stay.

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AP White House Correspondent Julie Pace and Associated Press writer Karl Ritter in Stockholm contributed.