London turned to the UN Security Council Wednesday and started freezing bilateral official contacts and suspending issuing of visas to Iranian officials.
"They [Britain] must understand that exerting pressure on Iran will yield no results. The issue of releasing the British female will meet difficulties, if the pressure continues," Ali Larijani, head of the National Security Supreme Council, said on TV.
On March 23, the U.K. Defense Ministry announced that Iran had detained 15 Navy sailors and marines from HMS Cornwall in Iraqi territorial waters, which in accordance with a UN Security Council mandate under Resolution 1723 was inspecting ships in the Persian Gulf.
Following Britain's claims, the Iranian Embassy in London issued a statement in which it said the sailors and marines had been 0.5 kilometers (0.3 miles) inside Iranian waters at the time.
Iran's Foreign Ministry accused the Royal Navy of illegally entering Iranian territorial waters.
Larijani said legal evidence should be provided to establish which of the parties was in the wrong and to resolve the problem.
"However, the British knew that the truth, namely illegally entering Iranian territorial waters by the British military, would be established, which is why they made such a fuss [about the sailors' detention] and started pressuring Iran," Larijani said.
Iranian media have reported that the female sailor has already offered an apology to Iranian authorities for illegally entering the country's territory.