"Our goal is to persuade the Iranian regime that they will actually be less secure if they proceed with their nuclear-weapons program," Clinton told a Senate subcommittee overseeing State Department funding.

"A nuclear-armed Iran with a deliverable weapons system is going to spark an arms race in the Middle East and the greater region," she told senators who asked about diplomatic strategy with Tehran if it accepts President Barack Obama's invitation to dialogue.

"That is not going to be in the interests of Iranian security. And we believe we have a very strong case to make for that," the chief US diplomat said.

Iranian President Mahmoud Ahmadinejad has repeatedly said his government intends to pursue its sensitive nuclear work, even at the risk of further international sanctions.

The Islamic Republic resumed in early 2006 its program to enrich uranium and has since refused to suspend it despite five UN Security Council resolutions, including three imposing sanctions.

After meeting Israeli Prime Minister Benjamin Netanyahu in Washington on Monday, US President Barack Obama said that he would assess whether Iran was serious about nuclear talks by the end of this year.

The United States, Israel and European powers fear the enrichment program is aimed at producing a nuclear weapon. Iran denies the charge, saying it is only for peaceful nuclear energy.

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