 Complete the following phrase:  Subsequently he was sent as Pakistan Ambassador to the United States in 1959 and was instrumental in developing the strong ties between the two countries, that characterised both the Eisenhower and the Kennedy administrations of the early sixties. He returned in 1963 to take up the post of Foreign Secretary at a time when Zulfikar Ali Bhutto was the Foreign Minister. He gained further prominence at the national level in Pakistan, following the 