Islamabad, Oct 27 Pakistan on Friday opposed the sale of US drone system to India, raising concerns that the move can potentially disrupt the balance of power in the region. "International powers must show responsibility before signing such agreements," said Pakistan Foreign Office spokesman Nafees Zakaria in his weekly press briefing. Zakaria said Pakistan and the US wished to strengthen relations but this should be based on better understanding of each other's concerns. "During US Secretary Rex Tillerson's visit to (Pakistan) and talks with the Prime Minister, bilateral and regional issues were discussed," he said. "He was informed about Pakistan's counter-terrorism operations and successes on which Tillerson acknowledged the country's contribution and sacrifices in the fight against terrorists and the country's strategic and economic importance in the region," he added.