Dominic Raab is seen at the Foreign and Commonwealth building after being appointed as the Foreign Secretary by Britain's new Prime Minister Boris Johnson in London, Britain, July 24, 2019. Dan Kitwood/Pool via REUTERS

BANGKOK (Reuters) - Britain on Thursday ruled out exchanging an Iranian tanker detained by Gibraltar for a British-flagged tanker seized by Iran in the Gulf.

“We are not going to barter: if people or nations have detained UK-flagged illegally then the rule of law and rule of international law must be upheld,” Foreign Secretary Dominic Raab said while on a trip to Bangkok.

“We are not going to barter a ship that was detained legally with a ship that was detained illegally: that’s not the way that Iran will come in from the cold,” he said. “So I am afraid some kind of barter or haggle or linkage is not on the table.”

Tensions have spiked between Iran and Britain since after Iranian commandos seized a British-flagged tanker last month. That came after British forces captured an Iranian oil tanker near Gibraltar, accused of violating sanctions on Syria.