Less than four days after he was sworn into office, Ashton B. Carter landed in Kabul early Saturday on his inaugural overseas trip as defense secretary to assess the progress of the war in Afghanistan and review possible changes to the timetable for withdrawing all U.S. troops from the country.

During a planned two-day visit, Carter is scheduled to meet with Afghan President Ashraf Ghani and U.S. military commanders, as well as to visit some of the 10,600 U.S. troops remaining in the country. High on his agenda: determining whether the Obama administration should revisit its plans for pulling out half of the U.S. force by the end of this year, and the rest by the end of 2016.

“We’re looking for success in Afghanistan that is lasting,” Carter told reporters traveling with him aboard a U.S. military aircraft shortly before he arrived in Kabul. “The best way to do that is precisely what I’m here to assess.”

Carter said he met with President Obama on Tuesday — the day he was sworn in as the fourth defense secretary of Obama’s tenure — and pledged to take a fresh look at plans to wind down U.S. involvement in the war.

“I promised the president that I would do that, that I would begin to get my own thinking together in this,” he said, “so that I can better inform his thinking.”

Secretary of Defense Ashton Carter, left, walks with Gen. John Campbell, who greeted him upon his arrival in Kabul. (Jonathan Ernst/AFP/Getty Images)

The U.S. military ended conventional combat operations in Afghanistan on Dec. 31, but U.S. troops remain in the country to train and assist about 350,000 Afghan security forces in their fight against the Taliban. U.S. commandos are also still conducting counter-terrorism operations, including night raids and drone strikes.

U.S. troop levels in Afghanistan are at a fraction of what they were four years ago, when they reached a peak of 100,000.

Army Gen. John F. Campbell, the commander of U.S. and NATO forces in Afghanistan, has recently floated proposals that would keep more U.S. troops in the country beyond the 5,500 that are currently slated to remain by the end of 2015.

U.S. officials have said they are not contemplating any changes to Obama’s promise to end the U.S. military mission completely by the time he leaves office in January 2017. But they are considering whether to revise their timetable for closing regional training hubs and a major base at Kandahar Airfield in southern Afghanistan. Carter is expected to confer closely throughout his visit with Campbell and Army Gen. Lloyd Austin, the commander of all U.S. forces in the Middle East and Afghanistan.

Ghani has urged the Obama administration and U.S. military leaders to adopt a more deliberate withdrawal schedule, saying that his government’s fledgling forces are still in need of as much U.S. training and assistance as they can get. Ghani, who took office last year, has developed a warmer relationship with officials in Washington than his predecessor, Hamid Karzai, who was eager to see U.S. and NATO troops leave.

Carter, a physicist by training, has held numerous posts at the Pentagon dating to the Jimmy Carter administration. He most recently served as deputy defense secretary — the number-two job at the Pentagon — until December 2013.

He was nominated by Obama to lead the Defense Department after his predecessor, Chuck Hagel, lost the confidence of the White House and was pushed to resign.