Britain on Thursday said that it would not exchange the Iranian tanker that had been detained by Gibraltar for a British-flagged tanker captured by Iran in the Gulf, Reuters reported.

“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,” the news agency quoted Britain’s Foreign Secretary Dominic Raab as saying. The foreign minister said that it was not going to exchange the ships, saying “that’s not the way that Iran will come in from the cold”.

On Tuesday, Iran’s ambassador to the United Kingdom Hamid Baeidinejad had said that the Iranian vessel’s release could also lead to the freedom of the British tanker. “Of course, one issue can help resolution of another issue but these are two separate issues that need to be tackled separately,” Sky News quoted him as saying. “We’re very keen to see the UK is doing all the measures necessary to release as soon as possible the Grace 1.” Iranian President Hassan Rouhani had also indicated on July 24 that he would release the tanker if the United Kingdom released theirs detained in Gibraltar.

The owners of the British-flagged ship, Stena Impero, on Tuesday had said that there was “growing concern” among the crew of the ship, which has been detained off the Iranian port of Bandar Abbas, according to BBC.

Tension between the two countries have continued after Islamic Revolutionary Guard Corps had seized the tanker o July 19 with 23 crew members, including 18 Indians, for allegedly violating international maritime regulations. This came after the Iranian Grace-1 oil tanker was seized on July 4 by Royal Gibraltar Police after being suspected to have broken European Union sanctions by transporting oil to Syria.