Obama's Republican presidential rival, John McCain, also wants three more brigades in Afghanistan and pledged to find the extra troops by "asking NATO to send more and by sending U.S. troops as they become available."
But despite the violence, many Afghanistan analysts doubted sending more troops was the answer.
"I don't think decreasing or increasing troop numbers is going to yield a long-term stability here, or peace," said Matt Waldman, policy adviser to Oxfam International.
More effective aid, rural development and conflict resolution at a local level are the real priorities, he said.
Foreign spending on aid and development is dwarfed by that spent on military operations in Afghanistan. The U.S. military alone now spends some $100 million a day, aid agencies say, compared with $7 million a day spent by all aid donors.
McCain criticised Obama for announcing his strategy on Afghanistan before leaving for the fact-finding trip.
"Apparently, he's confident enough that he won't find any facts that might change his opinion or alter his strategy. Remarkable," McCain said in his weekly radio spot.
"This is similar to the mistake Senator Obama made when he confidently declared that the surge in Iraq could not possibly reduce sectarian violence there," he said. "And it is precisely the success of the surge in Iraq that shows us the way to victory over the Taliban."
Asked whether he would have some tough talk for Afghan President Hamid Karzai and Maliki, Obama said: "I'm more interested in listening than doing a lot of talking.
"And I think it is very important to recognise that I'm going over there as a U.S. senator. We have one president at a time, so it's the president's job to deliver those messages."
Obama last week criticised Karzai in an interview with CNN.
"I think the Karzai government has not gotten out of the bunker and helped to organise Afghanistan," he said.
