While the United States has about four times more troops in Iraq than the 36,000 it has in Afghanistan, more of its soldiers were killed in Afghanistan in May and June than in Iraq.
More than six years after U.S.-led and Afghan forces toppled the Taliban for sheltering al Qaeda leaders behind the September 11 attacks, there has been a sharp rise in violence in recent months and there are few signs the insurgency is weakening.
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, one of the largest development agencies in Afghanistan.
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.
Asked whether he would have some tough talk for Afghan President Hamid Karzai and Maliki, Obama replied, "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, and the government, the judiciary, police forces, in ways that would give people confidence. So there are a lot of problems there," he said
Joining Obama in the congressional delegation were Jack Reed, a Democratic senator from Rhode Island, and Sen. Chuck Hagel, a Republican from Nebraska.
