Carter arrived in the war-torn country on Saturday which marks his first official visit since he took over the job on Tuesday.
Carter said that he plans to meet with Afghan and American officials to make sure "lasting” success is achieved as US troops are withdrawing from the country.
US-led foreign forces formally ended combat operations in Afghanistan in December, with only 13,500 troops remaining there in an advisory role.
"We’re looking for success in Afghanistan that is lasting, and the lasting accomplishment of our mission here," Carter told reporters shortly before landing in Kabul. "How to do that, what the best way to do that is, is precisely what I’m here to assess."
The Pentagon chief said he was told by President Barack Obama to carry out his own assessment of the situation in Afghanistan adding he would suggest "adjustments” if necessary.
Carter met with Afghan President Ashraf Ghani at the Presidential Palace in Kabul on Saturday and discussed the future of the US military presence in Afghanistan.
Carter said he was willing to get an update from Ghani, noting they would talk about peace efforts by Afghanistan with Taliban militants.
According to senior Pakistani, Afghan and diplomatic officials, the Afghan Taliban have voiced their readiness to start peace negotiations with Kabul.
Despite an official end to foreign combat mission in Afghanistan, the US is escalating a secret war in the country, according to a new report.
Washington has increased secret night raids in Afghanistan since October, when American and Afghan commandos found a laptop computer with files allegedly detailing planned terrorist attacks in Afghanistan and neighboring Pakistan, The New York Times reported last week.
The US and its allies invaded Afghanistan in 2001 as part of Washington’s so-called war on terror.