Pakistani officials say some 250,000 children in the country's northwest will likely not receive life-saving polio vaccinations due to threats from militants.

A three-day national anti-polio campaign is set to begin Monday.

Last month, a militant group warned anti-polio medical teams to stay away or “face consequences.” Militants allege the effort is being used to gather information for suspected U.S. drone strikes in the region.

The militant group cited the case of jailed Pakistani doctor Shakil Afridi, who was accused of running a fake vaccination campaign to help the CIA confirm Osama bin Laden's presence at a compound in Pakistan.

U.S. special forces killed the al-Qaida leader in a covert raid in May 2011.