NEW DELHI, Aug 8 (Reuters) - New Delhi has put on hold its plans to procure new U.S. weapons and aircraft, according to three Indian officials familiar with the matter, in India's first concrete sign of discontent after tariffs imposed on its exports by President Donald Trump dragged ties to their lowest level in decades. India had been planning to send Defence Minister Rajnath Singh to Washington in the coming weeks for an announcement on some of the purchases, but that trip has been cancelled, two of the people said. Trump on Aug. 6 imposed an additional 25% tariff on...