Romulo's schemes to discredit Guerrero had finally lost their power. Serrano appointed Guerrero member of the UN delegation for the Fourteenth Session of the General Assembly starting on 15 September 1959 headed by former Senator, now Ambassador Francisco Delgado, with Lopez as the vice-chair. He could have gone to the Twelfth Session when his name was removed from the list of members because Romulo insisted to Garcia to revoke the appointment. Prior to his departure, in the wake of the Serrano-Bohlen military bases negotiations, Guerrero urged Serrano via cable to advocate an affirmative SEATO action to the communist problem in Laos to test SEATO's reliability if the need arose in the Philippines.

At the United Nations in New York, Guerrero was having a good time when on the last day of September he got involved in a verbal tiff with Walter Robertson, a member of the American delegation and former Assistant Secretary of State for Far Eastern Affairs. At a U.S.-hosted diplomatic luncheon for the General Assembly's Special Political Committee in one of the U.N. dining rooms where diplomats from Japan, the Netherlands, Canada and several other nations were also seated, he was listening to Robertson on the issue of Tibet scheduled to be tackled in the following week. Then, he joined in saying that some Asian nations were hesitant to have a full-blown debate on Tibet because it would revive Cold War issues into the assembly when the East-West relations were starting to relax. The talk came to the issue of Communist China. Known for his pro-Chinese Nationalist views, Robertson boasted that the United States was the only defence against communist aggression and that he believed that countries had to avail themselves of “free world” security.

It turned to Philippine-American relations dealing with those irritants that continued to vex the bilateral relationship, but Robertson argued that America had taken an altruistic policy towards the Philippines. Guerrero replied that the Philippines offered parity rights in exchange for the war damage payments, where full settlement was still wanting. Robertson remarked that Guerrero's views echoed “the Recto line” to which Guerrero retorted, “I don't care if it is the Recto line. That's my line, too.” “You're not used to hearing Filipinos speak to you frankly,” he added, “You're used to listening to Romulo. You're used to hearing only what is pleasing to you.”