The U.S. troop withdrawal from Afghanistan has become a major selling point of Obama's re-election campaign.
"Change is the promise we made in 2008," Obama told supporters at a campaign fundraiser in Detroit last month. "For the first time in nine years, there are no Americans fighting in Iraq. We have refocused our efforts on the terrorists who actually attacked us on 9/11. Al Qaeda is weaker than it's ever been. Thanks to our amazing troops, Osama bin Laden no longer walks the face of this Earth."
"We have begun to transition out of Afghanistan. That's what change is," he said.
The latest ABC News/Washington Post poll found a record-high number -- 66 percent -- of Americans believe the Afghanistan war has not been worth fighting, matching opposition to the war in Iraq at its peak five years ago.
As for views of Obama's handling of the war effort, more Americans approve than disapprove of his leadership, 48 to 43 percent.
Tuesday's trip marks Obama's third visit to Afghanistan since he took office in 2009.
He most recently visited Kabul in December 2010, one year after approving a surge of U.S. troops to try and stabilize the war-torn country.
Obama made his first visit as president in March 2010, when he rallied U.S. troops and pressed Karzai in a private meeting to more forcefully combat government corruption and fight Islamic extremism.
ABC News' Luis Martinez, Gary Langer and Mary Bruce contributed to this report.