The vessel bearing oil was suspected of circumventing EU sanctions and was believed to be on its way to Syria, as per the United Kingdom. Iran has since slammed its vessel's seizure, demanding for its immediate release.
During the phone call, UK's Foreign Minister Jeremy Hunt assured Zarif that London would facilitate in getting the tanker released if given the guarantee that the vessel would not head to Syria.
Zarif, on the other hand, reiterated that Iran would continue selling its crude oil regardless of the circumstances, according to Iran's state news agency IRNA.
The Iranian leader is currently on his way to the United States to attend the annual meeting of the United Nations Economic and Social Council (ECOSOC). He will then head to Venezuela to attend the Non-Aligned Movement (NAM) foreign ministers' meeting, as per Iranian authorities, amongst other foreign engagements.
In the meantime, UK raised the level of threat to British shipping in Iranian waters to 'critical' on July 9. The country also claimed that Iran failed to halt a British oil tanker in the region -- an accusation which has since been dismissed by Tehran.