The UK government did not take its "eye off the ball" over the seizure of a UK-flagged oil tanker in the Gulf on Friday, the chancellor told the BBC.
Philip Hammond said the UK has been working closely with US and European partners in response to Iran's actions.
But ex-Tory party leader Iain Duncan Smith said the Stena Impero's capture was a "major failure" for the UK.
Iran's foreign minister said only "prudence and foresight" would reduce tensions between Iran and Britain.
The 23 crew members, who are Indian, Russian, Latvian and Filipino, have now been taken off the ship for "questioning", Iran's Press TV has reported.
Charts showing the ship was in Omani waters when it was captured prove its seizure was in "clear violation of international law", the UK Chamber of Shipping said.
The UK has accused Iran of "unacceptable and highly escalatory" action, in a letter to the president of the United Nations Security Council.
What have UK politicians said?
Speaking on the BBC's Andrew Marr programme, Mr Hammond said the UK would pursue "every possible diplomatic route" to resolve the situation.
He said sanctions, including financial, against Iran are already in place, and it was unclear what more could be done.
Mr Hammond, who announced his intention to resign if Boris Johnson becomes prime minister, added: "We are of course looking at all the options."
But Mr Duncan Smith told the BBC there are questions to be raised about the British government's behaviour.
He said the detention of a tanker carrying Iranian oil two weeks earlier ought to have served as a warning British vessels in the Gulf needed protection.