IN ADDITION to sitting down with Mr Medvedev, Mr Obama also is meeting with Mr Putin, the former president who now is prime minister but remains a major force.

'I think that it's important that even as we move forward with President Medvedev that Putin understand that the old Cold War approaches to US-Russian relations is outdated; that's it's time to move forward in a different direction,' Mr Obama said.

He said Mr Medvedev understands that, but Mr Putin needs convincing that the United States wants cooperation rather than 'an antagonistic relationship.'

On Afghanistan, Mr Obama said he intends to reassess the possible need for additional US troops after the nation holds national elections in August, but he believes America's key goals can be met there 'without us increasing our troop levels.'

He has ordered 21,000 more troops to Afghanistan this summer, bringing the US total to 68,000. He spoke on a day when 4,000 of those newly arrived US Marines stormed through southern Afghanistan and when news surfaced that an American soldier who disappeared after walking off his base in eastern Afghanistan was believed captured.

Mr Obama outlined his benchmarks for making any new decision about troops there: whether Al-Qaeda and other terror groups can set up havens in Afghanistan; whether the Afghan national army and police can secure the country without help; and whether the border with Pakistan can be made less porous.

'We can't tolerate a situation in which terrorist organizations act with impunity,' he said.

Minutes before his vice-president, Joe Biden, landed in Iraq for a two-day visit, Mr Obama said he was confident, but not certain, that the timetables for removing US troops from that war will hold.

This week marked a major milestone in the war when US troops pulled out of major Iraqi cities.

'I reserve the right to make changes based on changing circumstances to protect US security,' he said.

As for Guantanamo detainees, the former constitutional law teacher expressed doubts about his call to create a new legal framework to deal with terror suspects considered too dangerous to release but also impossible to prosecute. Such an action potentially would mark a major change in American jurisprudence.

'We're going to proceed very carefully on this front, and it may turn out that after looking at all the dimensions of this, that I don't feel comfortable with the proposals,' Mr Obama said. 'We don't have a tradition of detaining people without trial.'

He added: 'How we deal with those situations is going to be one of the biggest challenges of my administration.'

Mr Obama predicted that 'a sizable number of' the suspected terrorists and foreign fighters now being held without charge at the prison in Cuba would get their day in court, either in civilian federal courts or military tribunals.

With prospects for congressional approval of 'prolonged detention' murky, there has been talk that the White House might simply declare changes to be in effect. Mr Obama's predecessor, President George W. Bush, issued such an executive order, and Mr Obama ordered a review of the detentions of all those held under Mr Bush's order.

'I am not comfortable with doing something this significant through executive order,' Mr Obama said in Thursday's interview. -- AP