"Pakistan is in a very serious situation," Sharif told The Washington Post Friday. "I'm here to do what I can."
Sharif, who was overthrown by President Pervez Musharraf in a bloodless 1999 military coup, hopes to become a unifying force in the political turmoil following the assassination of former Prime Minister Benazir Bhutto, the report said.
Sharif said appointing Musharraf military chief was his only mistake when he was in power.
Sharif, 58, ended an eight-year exile and returned to Pakistan in November. He is urging Musharraf to resign and return to the bench independent judges removed by an emergency government decree.
"We need a return of the judges, a return to rule of law, a return to democracy," he said.
Sharif's Pakistan Muslim League-N party is popular in Pakistan but has not won backing from the United States, although U.S. diplomats in Islamabad have offered to meet with Sharif, the Post said.