India must be wary of Pakistanis who are trying to enter the county for nefarious reasons, a senior United States diplomat has said, during the first ever web-chat on popular social networking site Facebook."India must be wary of those Pakistanis seeking to enter India for nefarious reasons, but the signal India sent -- openness to a better relationship with peace-loving Pakistanis -- was a powerful message," said Gregg Sullivan, director of press and public diplomacy.