Obama, dressed in light khaki colored trousers and a checkered shirt with his sleeves rolled up, and others in the delegation received a briefing inside the U.S. base in Jalalabad from the Afghan provincial governor of Nangarhar, Gul Agha Sherzai, a no-nonsense, bullish former warlord.
"Obama promised us that if he becomes a president in the future, he will support and help Afghanistan not only in its security sector but also in reconstruction, development and economic sector," Sherzai told The Associated Press.
The area where the meeting took place is not far from where Osama bin Laden escaped U.S. troops in 2001 after his al-Qaida terrorist group led the attacks on Sept. 11. With the ousted Taliban regime resurgent and given the al-Qaida goal of terrorizing the U.S., Obama has argued that the war in Afghanistan deserves more attention as well as more troops.
Obama's first overseas tour since securing the Democratic nomination - he is scheduled to travel to Europe through next week - could be key to honing his foreign policy strategy with less than four months before the election. His rival for the presidency, Republican Sen. John McCain, has criticized Obama for not spending more time in the region and for developing a policy without more firsthand knowledge.
In that vein, Obama was expected to meet with Afghan President Hamid Karzai on Sunday.
Traveling with Obama were Sens. Chuck Hagel, a Nebraska Republican, and Jack Reed, a Democrat from Rhode Island. Both military veterans, the senators have been mentioned as potential Obama vice presidential running mates, although Reed has said he's not interested in the job and Hagel would be an unlikely cross-party choice.
At the start of their Afghan trip, the delegation met with top military leaders and troops at Bagram Air Field, the main U.S.
military base north of the capital, before going to Jalalabad Air Field in Nangarhar province.
Before departing the U.S., Obama said he wanted to see "the situation on the ground."
"I want to, obviously, talk to the commanders and get a sense both in Afghanistan and in Baghdad of, you know, what the most, their biggest concerns are, and I want to thank our troops for the heroic work that they've been doing," he said.
A lack of time in the region has not stopped Obama from proposing significant changes to the war effort in Iraq and Afghanistan.
Obama advocates ending the U.S. combat role in Iraq by withdrawing troops at the rate of one to two combat brigades a month. He supports increasing the military commitment to Afghanistan, where the Taliban-led insurgency is at its strongest in seven years.
In an interview with German magazine Der Spiegel released Saturday, Iraqi Prime Minister Nouri al-Maliki called Obama's suggestion of 16 months "the right timeframe for a withdrawal" and said U.S. troops should leave Iraq "as soon as possible." His statement was a sharp contrast to Bush administration policy, supported by McCain, opposing a set timetable for withdrawal.
U.S. military officials say the number of attacks in eastern Afghanistan, where most of the U.S. forces in the country operate, has gone up by 40 percent so far in 2008, compared to the same period in 2007.
The top U.S. commander in Iraq said Saturday that after intense U.S. assaults there, al-Qaida may be considering shifting focus to its original home base in Afghanistan, where American casualties are running higher than in Iraq.
"We do think that there is some assessment ongoing as to the continued viability of al-Qaida's fight in Iraq," Gen. David Petraeus told The Associated Press in an interview in Baghdad.
Obama has expressed frustration with Afghanistan's neighbor Pakistan's efforts to go after militants in its territory. He recently said that "If Pakistan cannot or will not act, we will take out high-level terrorist targets like bin Laden if we have them in our sights."
That stance may strike a chord with Karzai, who has directly accused Pakistan's intelligence service of supporting the Taliban insurgency plotting bombings and other attacks in Afghanistan - claims that Pakistan, a key U.S. ally in its war on terror, flatly denies.
But Obama has also chided Karzai and his government, saying it had "not gotten out of the bunker" and helped to organize the country or its political and security institutions.
Violence is spiraling in Afghanistan, although foreign troops numbers are at their highest since the invasion: about 60,000 in all, including 36,000 Americans. They are bolstered by a steadily growing number of Western-trained Afghan army soldiers.
Obama has proposed sending two more combat brigades - about 7,000 troops - to Afghanistan. McCain is also advocating sending more forces to the war-battered country.
As a reminder of the challenges in Afghanistan, authorities reported Saturday that a roadside bomb killed four policemen in the volatile south where the Taliban insurgency is centered. A NATO soldier also was reported killed.
Few citizens in impoverished Afghanistan were aware of Obama's unannounced visit, and few have been following the U.S. presidential race, being too busy eking out an existence amid soaring violence and with limited access to news media.
But some interviewed Saturday said they would welcome an Obama presidency if he could help their country end the fighting, corruption and poverty that have crippled it for so long.
"Obama is a good person," said Abdul Basir, 40, a former army officer. "During his campaign I heard he was saying that if I become president I will withdraw the U.S. troops from Iraq and bring them to Afghanistan and I will attack on the terror center on other side of border (in Pakistan). It is very important and I appreciated that."
En route to Afghanistan, Obama stopped Friday at Camp Arifjan, the main U.S. military base in Kuwait and a major gateway for U.S. soldiers moving into and out of Iraq.
In video released Saturday by the military, Obama said the troops needed the support of Congress as well as the public and that it was critical that "we also have a strategy and a mission that allows you to do your jobs well but is also going to serve the larger strategic interests of the United States."
Obama played basketball with some troops and joked to those watching, "You came out here because you wanted to see me get beat by your fellow soldiers."
