Israeli Prime Minister Ehud Olmert said on Thursday there would be a 'price to pay' if Iran does not agree a deal with world powers on its nuclear programme.
"The Iranians should be afraid -- they must understand if they object to every compromise there will be a price to pay," Olmert told reporters on a flight returning from Russia after a two-day visit there. He said time was running out for a deal.
"Time is not standing still. There comes a time when you have to do damage control. Perhaps there will be a need to do something in the future," he said without elaborating.
Tehran denies it is seeking an atomic bomb and says its nuclear programme is for electricity generation. Israel is widely believed to have nuclear arms but has never confirmed it.
Olmert said Iran as one of the key issues during his trip to Russia where he met Russian President Vladimir Putin and other senior officials.
"After all of my meetings I came out with a very strong feeling that Russia is definitely against a nuclear Iran," Olmert said.
Russia is building a nuclear power plant in Iran and has vowed to conclude the project despite US and Israeli pressure to halt it.
Olmert has said a nuclear-armed Iran, whose President Mahmoud Ahmadinejad has called for the destruction of the Jewish state, would pose an "existential threat" to Israel as well as its neighbours.
"I am not an extremist, but there is a range where you can try a compromise with Iran," Olmert told reporters. "I am not opposed to an acceptable agreement but we must set a red line which must not be crossed."
Olmert's visit to Russia coincides with the 15th anniversary of the establishment of diplomatic relations between the two countries.