Democratic presidential hopeful Barack Obama [Images] has advocated "tough, thoughtful and realistic" foreign policy for the US, and said that an open-ended commitment by Washington on Iraq was a "strategic mistake".

"I think that we have to have a clear sense of what our values are and what our ideals are. I don't think that we should shy away from being straight with the Russians about human rights violations," Obama said in an interview to CNN.

"We should not shy away from talking to the Chinese about those same subjects ... We have to be tough negotiators with them when it comes to critical issues," he said.

"We have to engage and get them involved and brought into dealing with some of these transnational problems. And that kind of tough, thoughtful, realistic diplomacy used to be a bipartisan hallmark of US foreign policy.

"And one of the things that I want to do, if I have the honour of being president, is to try to bring back the kind of foreign policy that characterised the Truman administration with Marshall and Acheson and Kennan," Obama said.

Harry S Truman was the US President from 1945 to 1953 -- the period marking the end of Second World War and beginning of the Cold War.

"We need to show leadership through consensus and through pulling people together wherever we can. There are going to be times where we have to act unilaterally to protect our interests. And I always reserve the right to do that, should I be commander-in-chief," he added.

Obama also criticised Bush administration for making an open-ended commitment to Iraq, saying it was a "mistake".

"I have been very careful not to put numbers on what a residual force would look like.What I'm absolutely convinced of is that, to maintain permanent bases, to have ongoing combat forces, to have an open-ended commitment of the sort that John McCain [Images] and (President) George Bush [Images] have advocated, is a mistake. It is a strategic mistake," Obama said.

"It weakens our ability to go after al-Qaeda in Afghanistan. It continues to fan anti-American sentiment. I think it allows Iran to more effectively engage in mischief... it prevents us from isolating them.... Those costs cannot be borne. And that's before we even start talking about the hundreds of billions of dollars and American lives that are lost or profoundly disrupted as a consequence of this engagement," he said.

"My job is to make sure that, here in the US, the American people feel confident that I'm going to be advocating for their interests, that I'm going to keep them safe. The way to do that though, I believe, is to make sure that we're  paying attention to the rest of the world, their hopes, their aspirations, as well, and that we're leading with our values and ideals, and not just with our military," Obama added.