Democratic presidential candidate Barack Obama arrived in Afghanistan on Saturday, on the first leg of a trip aimed at proving his foreign policy credentials that will also take in the Middle East and Europe.

Obama's trip to Afghanistan, Iraq, Jordan, Israel, Germany, France and Britain is meant to prove he can credibly navigate the minefield of international diplomacy and answer critics who say he is too inexperienced for the task of commander-in-chief.

Just before boarding a military plane for the trip, Obama told reporters he expected to do a lot of listening.

"I want to, obviously, talk to the commanders and get a sense, both in Afghanistan and in Baghdad of ... what ... their biggest concerns are. And I want to thank our troops for the heroic work that they've been doing," Obama said.

He wants to send two more brigades, or about 7,000 U.S. troops, to Afghanistan and a shift from what he called the Bush administration's "single-minded" focus on Iraq. He has called for removing U.S. combat troops from Iraq in 16 months.

Iraqi Prime Minister Nuri al-Maliki said whether Obama or his Republican rival John McCain won the November 4 election, pulling out troops in the shorter term would be better for Iraq.

Asked in an interview with Germany's Der Spiegel magazine when U.S. troops should leave Iraq, he said:

"As far as we are concerned, as soon as possible. U.S. presidential candidate Barack Obama talks about 16 months. That, we think, would be the right timeframe for a withdrawal, with the possibility of slight changes," Maliki said.

OBAMA "LISTENING, NOT TALKING"

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.