What happened
At the UN, Adlai Stevenson challenged Soviet representative Valerian Zorin over the deployment. The tanker Bucharest was allowed through the quarantine. U Thant sought a pause, but Washington remained concerned that construction on the island would continue during negotiations.
Sources for this passage: [1]Public proof and selective enforcement
At the United Nations, Adlai Stevenson challenged Soviet representative Valerian Zorin and presented photographic evidence of the deployment. The exchange brought material previously examined in secret briefings before an international audience. Establishing that the missiles existed was part of the contest for diplomatic support.
At sea, the tanker Bucharest was allowed to continue after surveillance without a boarding. This was consistent with a selective quarantine aimed at prohibited weapons rather than a ban on all trade. Meanwhile, U Thant’s proposals for a pause faced the central American objection: negotiations must not simply give crews more time to complete the missile sites.
Sources for this passage: [1] [2]