U.S. Defense Secretary Chuck Hagel arrived in the Afghan capital Friday night to take stock of America’s winding-down war in Afghanistan, one of the thorniest issues the new Pentagon chief will confront. 

Just days after weathering a bruising confirmation process, the former Republican senator said he was eager to get a firsthand look at the war zone, speak to commanders and reacquaint himself with Afghanistan’s president, Hamid Karzai

“We have a lot of big issues and challenges ahead as we prepare for a responsible transition,” Hagel told reporters during the flight to Kabul. “That transition has to be done right. It has to be done in partnership with the Afghans, with our allies. Our country as well as the region and the Afghans have a lot at stake here, and our continued focus and energy and attention on Afghanistan is going to be very important.” 

The trip, which was not announced in advance because of security concerns, comes at a delicate time. U.S. officials continue to debate the role and mission the United States should aspire to have in Afghanistan in the long run — a process that has become knottier as Karzai has sought to rein in the authority of American troops in recent weeks. 

The secretary’s arrival coincided with the latest insider killing by Afghan security personnel. The NATO coalition said in a statement Friday night that individuals wearing Afghan army uniforms opened fire on NATO troops in eastern Afghanistan, killing a coalition contractor. The statement provided no additional details. 

Hagel’s first foray onto the international stage will no doubt be closely watched by supporters and critics of the veteran politician, whose lackluster and unsteady performance during last month’s confirmation hearing raised questions about whether he was the right person to take the helm of the Pentagon.

Hagel told reporters traveling with him that the White House has not yet decided how many troops it would like to leave in Afghanistan after 2014, when the mandate that authorizes an international military coalition here would have to be replaced by a bilateral security agreement.

“The president has not made a final decision,” he said. 

He stressed later, though, that while trying to help the Afghan people start a prosperous new era in the wake of the Sept. 11, 2001, attacks was a noble effort, “it was never the intention of the United States to stay in Afghanistan indefinitely.” 

Hagel last visited the country in 2008, when he was a senator from Nebraska, as part of a congressional delegation that included then-Sen. Barack Obama. 

Afghanistan received relatively little attention during Hagel’s confirmation process, which became fraught as Republican senators raised concerns about the nominee’s views on Iran, Israel and nuclear deterrence. Asked whether he was concerned that Afghanistan had become a “forgotten war,” Hagel said he would ensure war policy remains a priority. 

“I can’t speak for the American people or where we are on attention span,” he said. “I will tell you, now as secretary of defense who has some responsibility for assuring this transition be conducted responsibly, that we are still at war.” 

Hagel said he looked forward to talking to Karzai, who in recent weeks rankled American officials by issuing abrupt edicts. Karzai prohibited Afghan commanders from calling on the international coalition to carry out airstrikes and ordered U.S. special operations forces to abandon a key eastern province along the Pakistani border after accusing them of carrying out crimes. 

In a statement distributed to U.S. troops in Afghanistan after Hagel arrived, the defense chief said the campaign was “at a very important moment, with Afghan troops poised to play a leading role as a new springtime violent period dawns.”

“As the 2013 fighting season gets underway,” the statement said, Afghan forces “will be doing more and more of the fighting and relying on you for support, training and advice.”

Hagel added that the campaign’s mission, having the Afghan government achieve full responsibility for security by the end of 2014, was “clear and achievable.” 

Hagel, a former noncommissioned officer in the Army, said it was not easy to draw a parallel between the winding down of the war in Afghanistan and end of the Vietnam War, in which he served. 

“The only thing I would say is: The world we live in today is so complicated,” Hagel said. “We have to factor that into our policies and everything we do.”