US President Barack Obama confirmed on Tuesday that he would go to Russia this fall for a G20 summit but said he was "disappointed" that Russia granted temporary asylum to former US spy agency contractor Edward Snowden.

Speaking on NBC's "The Tonight Show" with host Jay Leno, Obama said Moscow sometimes slipped into a Cold War mentality, despite being cooperative with the United States on some issues, including counterterrorism efforts in the aftermath of the Boston Marathon bombing.

Obama was not asked and did not mention whether he would attend a separate meeting with Russian President Vladimir Putin during his Russian trip. That meeting was put in question after Moscow rejected US pleas and granted Snowden a year's asylum. The White House has said it is evaluating whether a one-on-one with Putin makes sense.

Washington wants Snowden, who was in hiding in Hong Kong before flying to Moscow in June, to be sent home to face criminal charges including espionage for disclosing secret American internet and telephone surveillance programmes.

"There have been times where they slip back into Cold War thinking and a Cold War mentality," Obama said of Russia.

"What I say to President Putin is, that's the past and ... we've got to think about the future. And there's no reason why we shouldn't be able to cooperate more effectively than we do."

During the interview, Obama also said the recent threat that caused the United States to close its embassies throughout the Middle East was significant.

"It's significant enough that we're taking every precaution," Obama said.

"It's a reminder that for all the progress we've made ... this radical, violent extremism is still out there," Obama said. "We've got to stay on top of it."

The US State Department issued a worldwide travel alert on Friday warning Americans that Al Qaeda may be planning attacks in August, particularly in the Middle East and North Africa. It initially announced the embassy closures would be only for Sunday, then extended the closures of some by a week.

Asked whether the controversial surveillance programmes helped lead to the intelligence that sparked the warnings, Obama said the programmes were critical to counterterrorism work. But he said more needed to be done to assure Americans they were not being spied on themselves.

"We don't have a domestic spying programme," he said. "What we do have are some mechanisms where we can track a phone number or an email address that we know is connected to some sort of terrorist threat."

The odds of dying in a terrorist attack were less than dying in a car accident, Obama said, and Americans should be careful but did not need to cancel planned vacations to places such as Europe as a result of the recent travel warnings.

LIGHTER SIDE

In lighter notes, Obama said he had invited his former secretary of state, Hillary Clinton, to her recent lunch at the White House and described her as having a post-administration "glow."

"We have become genuinely close, and I could not have more respect for her," Obama said.

Asked by Leno whether the former first lady and potential 2016 presidential candidate had "measured the drapes" while she was there, Obama said no.

"Keep in mind she's been there before," he joked. "She doesn't have to measure them."

Obama also confirmed - more or less - a budding "bromance" with his former 2008 presidential rival, Republican Senator John McCain, who has been supportive of Obama's push to reform US immigration laws.

"That's how a classic romantic comedy goes, right? Initially you're not getting along and then you keep on bumping into each other," Obama joked.

"John McCain and I have, you know, a number of philosophical differences, but he is a person of integrity. He is willing to say things regardless of the politics."

Leno also poked fun at Obama for having told a group of young people that broccoli was his favorite food.

"Me and broccoli, I don't know, we've got a thing going," Obama offered. - Reuters