Iran's first vice-president warned on Tuesday that the flow of crude will be stopped from the crucial Strait of Hormuz in the Gulf if foreign sanctions are imposed on its oil exports, the country's official news agency reported.

"If they (the West) impose sanctions on Iran's oil exports, then even one drop of oil cannot flow from the Strait of Hormuz," IRNA quoted Mohammad Reza Rahimi as saying.

About a third of all sea-borne oil was shipped through the Strait in 2009, according to the U.S. Energy Information Administration (EIA), and U.S. warships patrol the area to ensure safe passage.

Tensions over Iran's nuclear program have increased since the International Atomic Energy Agency (IAEA) reported on Nov. 8 that Tehran appears to have worked on designing a nuclear bomb and may still be pursuing research to that end. Iran strongly denies this and says it is developing nuclear energy for peaceful purposes.

Iran has warned it will respond to any attack by hitting Israel and U.S. interests in the Gulf, and analysts say one way to retaliate would be to close the Strait of Hormuz.

Most of the crude exported from Saudi Arabia, Iran, the United Arab Emirates, Kuwait and Iraq - together with nearly all the liquefied natural gas from lead exporter Qatar - must slip through a 4-mile (6.4 km) wide shipping channel between Oman and Iran.