Pakistan Prime Minister Nawaz Sharif on Monday cancelled his upcoming visit to the United States where he was scheduled to attend the Nuclear Security Summit.
Ehsanullah Ehsan said that he will release a detailed statement later in which he will mention the agreement he made with the Pakistani security authorities.
Over 300 people were also injured in the attack and many of them were in a critical condition.
Pakistani Taliban's splinter group Jamaat-ul-Ahrar on Thursday identified a 25-year-old man as the suicide bomber who blew himself up at Wagah killing 61 people, minutes after the popular flag-lowering ceremony at the main land border crossing with India.
IS, especially active in northern Sindh and Balochistan, was also behind the abduction and killing of two Chinese nationals last year.
Pakistan's Punjab government has said that the involvement of a "foreign hand" could not be ruled out in the Wagah Border suicide bombing, even after three homegrown militant factions separately claimed responsibility for the attack that killed at least 61 people.
Over 25,000 protesters had entered and besieged Islamabad's high-security zone on Sunday, damaging public buildings and breaking barriers that had been erected.
The United States identified LeT as one of the largest and most active terrorist organisations in South Asia.
The spokesman even taunted Prime Minister Nawaz Sharif on Twitter. "After the Lahore attack, Nawaz Sharif repeated old words to give himself false assurances," he wrote.