Foreign secretary says all options are on table but that aim is to get Tehran round negotiating table over nuclear weapons.
Britain has not ruled out military action against Iran but is focused on trying to secure peaceful negotiations, William Hague said.
The foreign secretary insisted all options remained on the table in relation to what he called Tehran's "increasingly dangerous" development of nuclear weapons. But he said the UK was not advocating military action and was instead intensifying sanctions in a bid to bring the Islamic republic to the negotiating table.
"We have never ruled anything out. We have not ruled out any option, or supporting any option. We believe all options should be on the table, that is part of the pressure on Iran," Hague told Sky News.
"But we are clearly not calling for or advocating military action. We are advocating meaningful negotiations, if Iran will enter into them, and the increasing pressure of sanctions to try to get some flexibility from Iran."
Western governments, including Britain, have moved to step up sanctions over Iran's nuclear programme, threatening an embargo on vital oil exports. Tehran has threatened to block the Straits of Hormuz oil shipment route in response.
The prime minister, David Cameron, warned Iran during a visit to Saudi Arabia on Friday that the world would "come together" to ensure the straits remained open.
Hague said: "This is an increasingly dangerous situation that Iran is developing a military nuclear programme. Our sanctions are part of getting Iran to change course and to enter negotiations and we should not be deterred from implementing those."