"Our focus is Nawaz Sharif's government," Ansar ul Mujahideen said yesterday.
"But 'we will turn our guns on' Khan if polio campaign continues," Newsweek Pakistan reported the group as saying.
The banned militant groups had earlier carried out attacks on anti-polio workers.
Pakistan Tehreek-e-Insaf leader Khan had earlier appealed to the Pakistani Taliban and others not to attack vaccination workers and pledged to spearhead the polio vaccination campaign in the restive northwest that continues to be in the grip of the crippling disease.
Militant groups have termed the polio campaign as an attempt to "sterilise Muslims" besides being used for spying.