Tehran, Iran ? Supreme leader Ayatollah Ali Khamenei said Sunday that Western accusations Iran seeks nuclear weapons are a “sheer lie,” and he declared that attempts to punish Tehran would jeopardize the world’s oil supply.

The implied threat was dismissed by Secretary of State Condoleezza Rice, who said Iran was too dependent on oil revenues to disrupt the flow of crude. She also put Iran on notice that the incentives offered by the West to suspend its nuclear program are not open-ended, although she declined to say Tehran had a firm deadline to respond.

Khamenei, who has the final say on all state matters, made his comments in a speech broadcast live on state radio.

“If you make any mistake (punish or attack Iran), definitely shipment of energy from this region will be seriously jeopardized,” Khamenei said, addressing Western nations.

Khamenei said the United States and its allies would be unable to secure oil shipments passing out of the Gulf through the strategic Strait of Hormuz to the Indian Ocean. At its narrowest point, the strait separating Iran from the Arabian peninsula is 44 miles wide.

“You will never be able to protect the energy supply in this region. You will not be able to do it,” he said.

Khamenei, however, did not specify how oil supplies would be disrupted, and he insisted to the assembled throng that Iran would not be “the initiator of war.”

In a television interview later Sunday, Rice sought to play down Khamenei’s remarks.

“I think that we shouldn’t place too much emphasis on a threat of this kind,” she said on “Fox News Sunday.” “Obviously it would be a very serious problem for Iran if oil were to be disrupted on the market.”

Last week, Rice said the U.S. was prepared to join the European Union and Germany in negotiations with Iran only if Tehran agreed to stop enriching uranium. The Western nations fear Iran is using what it calls a peaceful civilian nuclear program as a cover to build atomic weapons.

Khamenei said Iran was not a threat to any country.

“We have not threatened any neighbor,” he said, calling the accusation that Iran is seeking an atom bomb “a sheer lie.”