Sharif was initially scheduled to travel to Lahore from Islamabad via the famous Grand Trunk Road on Sunday, but the rally was postponed to Wednesday.
Pakistani security forces killed four Taliban militants in the eastern city of Lahore hours after a truck bomb killed one person and wounded 22, authorities said on Tuesday.
The blast also left a 10-15 feet crater on the spot. A rescue official told PTI that an explosive device planted in the truck went off at around 9pm local time.
Pakistan Police and its investigative agencies are yet to determine the kind of explosive material used in the incident.
American nationals should stay away from the area in the city of Lahore, Pakistan, where a bomb blast wounded scores of people earlier on Monday, according to the US State Department.
The injured were taken to Services and Mian Munshi hospitals from where 12 of them were discharged after first aid. "A minor girl is stated to be critical", he said. Dr Ashraf said that all aspects of the incident would be investigated to ascertain the real cause of the explosion.
She said the men, in their 40s, were present in the school building when it collapsed because of the impact of the blast. A number of bikes and cars were damaged due to its intensity.
Lahore, the capital of Pakistan's Punjab province, has seen a string of blasts in recent days.
The police and rescue teams have been rushed to the site.
In February, a suicide bomber killed 14 people, including senior police officers, near the Punjab Assembly here.