Iran will back any group or nation that attacks Israel, its supreme leader has warned.
Ayatollah Ali Khamenei told Iranians in a televised address that Iran would help enemies of Israel in the "fight against the Zionist regime".
He upped the anti-Israel and US rhetoric after the launch of a satellite that has already increased concerns about Iran's military ambitions.
"Threatening Iran and attacking Iran will harm America," Khamenei said. "The war would be 10 times [worse] against the interests of the US."
The satellite was launched after the EU went ahead with tough economic sanctions, including an embargo on Iranian oil exports. Iran threatened to take revenge by shutting down the Strait of Hormuz, through which one-fifth of the world's crude oil is transported from the Persian Gulf.
"Sanctions will not have any impact on our determination to continue our nuclear course," said Khamenei. "In response to threats of oil embargo and war, we have our own threats to impose."
Deputy Prime Minister Nick Clegg said the US and Israel could launch a military strike against Iran.
When asked about the likelihood of Israel attacking Iran, Clegg said: "I worry that there will be a military conflict and that certain countries might take matters into their own hands."
However, Clegg said he would not tell whether Britain would take part in any military action.
Israeli deputy minister Moshe Ya'alon claimed that Iran was successfully building long-distance ballistic missiles. He said the weapons were aimed at the US but missiles of a 6,200 mile-range could also strike the UK.