ANKARA, Turkey — The formula Ankara and Tehran crafted to bypass international sanctions on Iran and keep their oil and gas deals going has become a potential source of tension between the two neighbors. A major factor in this is Iranian President Hassan Rouhani’s strategy to mend fences with the West to have the sanctions lifted and re-integrate Iran into the global economy and international community.

The formula was the joint work of Mahmoud Ahmadinejad, Rouhani’s predecessor who defied the West and coveted nuclear weapons, and Turkey’s Recep Tayyip Erdogan, then prime minister and now president.

Shut out from the international banking system and thus unable to receive gas and oil payments in foreign currency, Iran was made an offer to be paid in gold through a gold account. With other Turkish banks reluctant to get involved, the task was given to the state-run Halkbank.

A central bank regulation that allowed banks to keep their required reserve ratios in gold provided legal grounds for the plan. Turkish gold exports abruptly boomed. Money of unknown origin and illicit earnings were easily funneled into the banking system through gold accounts, since anyone was permitted to deposit gold without specifying its origin.