Over 45 people were killed in Sunday's blast in the Abbas Town section of the seaside town that is Pakistan's main military and commercial maritime port into the Arabian sea, according to recent reports.
U.S. and NATO forces are depending heavily on those shipping ports to move over a decade's worth of vehicles, equipment and material stockpiled in Afghanistan.
On Monday, Pentagon Press Secretary George Little downplayed the threat Sunday's bombing would have on American withdrawal plans.
Current and future "shipments [of U.S. equipment] out of Karachi are as secure as possible," Little told reporters at the Pentagon, indicating the recent attack had not prompted any change to Department of Defense strategy for the Afghan withdrawal.
No specific group has claimed responsibility for the attack, which also wounded 150 civilians during evening prayers at a Shia mosque in the city, the BBC reports. However, Sunni militant organizations operating in southern Pakistan are suspected of launching the deadly strike.
Initial shipments of American supplies and equipment have already begun their slow journey out of Afghanistan to the United States via land-based supply lines in Pakistan.
Over 50 containers loaded down with U.S. weapons and material began crossing the Afghan-Pakistan border in February, marking the beginning of the logistical piece of the U.S. drawdown in Afghanistan.
Hundreds of shipments are expected to come through those supply routes toward Karachi over the next year, where they will be shipped back to military bases in the U.S.
Over half of the 66,000 American troops in Afghanistan are scheduled to begin rotating back to the U.S. this spring, in preparation for the White House's 2014 deadline to have all U.S. combat troops out of the country.
The remaining 32,000 U.S. forces in the country will begin their final drawdown after next April's presidential elections, former Defense Secretary Leon Panetta told NATO leaders in February at the alliance's headquarters Brussels.