President Barack Obama paid a surprise visit to Afghanistan late on Friday and assured cheering US troops they are winning the war against the Taliban despite "difficult days ahead."
The president landed in Kabul under cover of darkness, with aides announcing nothing of the trip beforehand due to security concerns.
Obama, who has tripled US troop numbers in Afghanistan, spent a mere four hours in the country during his second visit as president, all at this air base outside Kabul.
A face-to-face visit with President Hamid Karzai was replaced with a 15-minute phone call, as weather scuppered plans to fly Obama by helicopter to the nearby Afghan capital.
The trip came as the Obama administration faced new friction with Karzai over embarrassing assessments of the Afghan leader in leaked diplomatic cables, but war czar Douglas Lute told reporters the topic did not come up between the two leaders.
The White House is also preparing to release a review of its war strategy later this month to an American public increasingly weary of the nine-year conflict.
"You're achieving your objectives, you will succeed in your mission," Obama told nearly 4,000 exuberant troops who greeted him with cheers and applause.
"We said we were going to break the Taliban's momentum. That's what you're doing."
But Obama warned "there are going to be difficult days ahead" in the fight against insurgents, and appeared to choke up as he described his visit to a base hospital where he pinned Purple Heart medals on five wounded soldiers spending the holiday season on the battlefront.
A year after Obama authorized a surge of 30,000 US troops, Afghanistan is in the grips of growing violence that is deadlier than ever before. More than 1,400 US servicemen and women have been killed since the 2001 US-led invasion to oust the Taliban -- a third of them this year alone.
Amid uncertain signs of progress, the US military has held off on plans for a major offensive on the key city of Kandahar, a Taliban stronghold.
The president also spoke to a platoon that recently lost six of its members in an attack.
"I don't need to tell you this is a tough fight," Obama said.
But he stressed that "today we can be proud that there are fewer areas under Taliban control, and more Afghans have a chance to build a more hopeful future."
Obama noted that since his last visit in March, the allied coalition had grown by six to 49 countries, which he called a "powerful message" of support for the war-torn nation.
"We will never let this country serve as a safe haven for terrorists who would attack the United States of America again," he added.
"This part of the world is a center of a global effort where we are going to disrupt and dismantle and defeat Al-Qaeda and its extremist allies, and that's why we're here."
Sporting a leather bomber jacket, Obama was met by US ambassador Karl Eikenberry and war commander General David Petraeus, who Obama praised as an "extraordinary warrior."
"This is somebody who has helped change the way we fight war, and win wars, in the 21st century," he added.
After his address, Obama shook hands and took pictures with several hundred troops at a ropeline, and received a briefing from US Special Forces before departing early Saturday.
During a summit in Lisbon last month, the NATO alliance backed Obama's goal of handing over security to the Afghan police and military by mid-2011, with a view to ceding full control by the end of 2014.
During their call, Obama and Karzai "both acknowledged that early 2011 is not far off and that this has to remain a priority for both of them, to begin the transition process," Lute said.
Some 100,000 US troops are fighting in Afghanistan as part of Obama's ramped-up strategy to battle insurgents, nine years after the United States ousted the Taliban regime for harboring September 11 attack mastermind Osama bin Laden.
Obama sought to personalize the service and sacrifice of the troops before him at Bagram, citing a soldier who received the Medal of Honor for his service in Afghanistan and who called each of his military colleagues heroes.
"He's right," Obama said of Staff Sergeant Salvatore Giunta. "Each of you have your own story. Each of you is writing your own chapter with the story of America... Each of you have losses. Each of you have made sacrifices."
White House aide Ben Rhodes said the White House began preparing the Kabul visit more than a month ago as Obama wanted to visit US troops and civilians in Afghanistan between Thanksgiving and Christmas.
But the trip followed the latest release by WikiLeaks, in which secret US diplomatic cables showed renewed US questions about Karzai's leadership and rising concerns about corruption.
The December review by the White House will be an update on the US strategy, though officials cautioned that recommendations for major changes were unlikely.
"I don't think you'll see any immediate adjustments... Our charter was essentially diagnostic, meaning that the fundamental question we were charged to assess is, is this approach working?" Lute explained.
Rhodes said Obama would likely give a speech where he would "frame where we are, what we've learned about the strategy, what we've learned about what's working and about areas where we need to put additional emphasis going forward."