Israel's military chief says he doubts diplomatic efforts will prevent Iran from obtaining nuclear weapons.
Iran says its nuclear programme is for purely peaceful purposes
Lt-Gen Dan Halutz said Iran had managed to fend off international pressure "time after time".
Gen Halutz said there were military options available to block Iran's nuclear project, but that these were not being considered yet.
Some Western countries suspect Iran of trying to develop nuclear weapons, but Tehran says its programme is peaceful.
It says it has the right to enrich uranium and use it to generate energy.
However, enriched uranium can also be used in nuclear bombs.
The EU, with the backing of the US, has been leading efforts to persuade Iran to give up its enrichment attempts.
However, they have not yet roused enough international support to take the matter to the UN Security Council for possible sanctions.
"The fact that the Iranians are successful time after time in getting away from international pressure... encourages them to continue their nuclear project," Gen Halutz said.
IRAN'S NUCLEAR STANDOFF
September 2002: Work begins on Iran's first nuclear reactor at Bushehr
December 2002: Satellite photographs reveal nuclear sites at Arak and Natanz. Iran agrees to an IAEA inspection
September 2003: IAEA gives Iran weeks to prove it is not pursuing atomic weapons
November 2003: Iran suspends uranium enrichment and allows tougher inspections; IAEA says no proof of any weapons programme
June 2004: IAEA rebukes Iran for not fully co-operating with nuclear inquiry
November 2004: Iran suspends uranium enrichment as part of deal with EU
August 2005: Iran rejects EU proposals and resumes work at Isfahan nuclear plant
"I believe that the political means that are being used by the Europeans and the Americans to convince the Iranians to stop will not end in stopping them."
"The Iranians are determined to get a nuclear capability. From Israel's viewpoint such a situation is unacceptable."
There are military options to deal with Iran, he said, but those "alternatives are not being considered yet".
Israeli Prime Minister Ariel Sharon repeated that Israel would not allow Iran to become nuclear-armed.
"I hope that Iran will be brought soon before the Security Council and sanctions will be imposed against her so that the nuclear process will stop," he said.
He said Israel was a "partner" in attempts to block Iran's programme, but was not leading them.
Iranian foreign ministry spokesman Hamid Reza Asefi said on Sunday he believed a resumption of talks with the EU - suspended when Iran restarted uranium conversion in August - could yield "important results".
But he rejected the notion of direct talks with the US.