At the same time, the US State Department has lifted ordered departure status of non-emergency US government personnel from its Consulate in Lahore.
Consular services at the US Consulate in Lahore will remain unavailable but the US Embassy in Islamabad and the US Consulate General in Karachi will continue to provide routine consular services for American citizens.
"The Department of State warns US citizens to defer all non-essential travel to Pakistan. This Travel Warning replaces the Travel Warning dated September 6, 2013, to remind US citizens of ongoing security concerns in Pakistan," the State Department said.
Attacks have included armed assaults on heavily guarded sites, including Pakistani military installations.
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The Government of Pakistan maintains heightened security measures, particularly in the major cities.
Threat reporting indicates terrorist groups continue to seek opportunities to attack locations where US citizens and Westerners are known to congregate or visit.
Terrorists and criminal groups regularly resort to kidnapping for ransom, it said.