structural:scholar_edition, structural:summarization
U.S.–Iran tensions in 2011–2012

On 27 December 2011, Iranian Vice President Mohammad-Reza Rahimi threatened to cut off oil supply from the Strait of Hormuz should economic sanctions limit, or cut off, Iranian oil exports. A U.S. Fifth Fleet spokeswoman said in response that the Fleet was "always ready to counter malevolent actions", whilst Admiral Habibollah Sayyari of the Islamic Republic of Iran Navy claimed that cutting off oil shipments would be "easy". Despite an initial 2% rise in oil prices, oil markets ultimately did not react significantly to the Iranian threat, with oil analyst Thorbjoern Bak Jensen of Global Risk Management concluding that "they cannot stop the flow for a longer period due to the amount of U.S. hardware in the area".

On 3 January 2012, Iran threatened to take action if the U.S. Navy moves an aircraft carrier back into the Persian Gulf. Iranian Army chief Ataollah Salehi said the United States had moved an aircraft carrier out of the Persian Gulf because of Iran's naval exercises, and Iran would take action if the ship returned. "Iran will not repeat its warning...the enemy's carrier has been moved to the Gulf of Oman because of our drill. I recommend and emphasize to the American carrier not to return to the Persian Gulf", he said.

The U.S. Navy spokesman Commander Bill Speaks quickly responded that deployment of U.S. military assets would continue as has been the custom stating: "The U.S. Navy operates under international maritime conventions to maintain a constant state of high vigilance in order to ensure the continued, safe flow of maritime traffic in waterways critical to global commerce."

While earlier statements from Iran had little effect on global oil markets, coupled with the new sanctions, these comments from Iran are driving crude futures higher, up over 4%. Pressure on prices reflect a combination of uncertainty driven further by China's recent response – reducing oil January 2012 purchases from Iran by 50% compared to those made in 2011.

The U.S. led sanctions may be "beginning to bite" as Iranian currency has recently lost some 12% of its value. Further pressure on Iranian currency was added by French Foreign Minister Alain Juppé who was quoted as calling for more "strict sanctions" and urged EU countries to follow the US in freezing Iranian central bank assets and imposing an embargo on oil exports.

On 7 January 2012, the British government announced that it would be sending the Type 45 destroyer HMS Daring to the Persian Gulf. Daring, which is the lead ship of her class is one of the "most advanced warships" in the world, and will undertake its first mission in the Persian Gulf. The British Government however have said that this move has been long-planned, as Daring will replace another Armilla patrol frigate.

On 9 January 2012, Iranian Defense Minister Ahmad Vahidi denied that Iran had ever claimed that it would close the Strait of Hormuz, saying that "the Islamic Republic of Iran is the most important provider of security in the strait... if one threatens the security of the Persian Gulf, then all are threatened."

The Iranian Foreign Ministry confirmed on 16 January 2012 that it has received a letter from the United States concerning the Strait of Hormuz, "via three different channels." Authorities were considering whether to reply, although the contents of the letter were not divulged. The United States had previously announced its intention to warn Iran that closing the Strait of Hormuz is a "red line" that would provoke an American response. Gen. Martin E. Dempsey, the chairman of the Joint Chiefs of Staff, said this past weekend that the United States would "take action and re-open the strait", which could be accomplished only by military means, including minesweepers, warship escorts and potentially airstrikes. Defense Secretary Leon E. Panetta told troops in Texas that the United States would not tolerate Iran's closing of the strait. Nevertheless, Iran continued to discuss the impact of shutting the Strait on world oil markets, saying that any disruption of supply would cause a shock to markets that "no country" could manage.

By 23 January, a flotilla had been established by countries opposing Iran's threats to close the Hormuz Strait. These ships operated in the Persian Gulf and Arabian Sea off the coast of Iran. The flotilla included three American aircraft carriers (the USS Carl Vinson, the USS Enterprise and USS Abraham Lincoln) and three destroyers (USS Momsen, USS Sterett, USS Halsey), seven British warships, including the destroyer HMS Daring and a number of Type 23 frigates (HMS Westminster, HMS Argyll, HMS Somerset and HMS St Albans), and a French warship, the frigate La Motte-Picquet.

On 24 January, tensions rose further after the European Union imposed sanctions on Iranian oil. A senior member of Iran's parliament said that the Islamic Republic would close the entry point to the Persian Gulf if new sanctions block its oil exports. "If any disruption happens regarding the sale of Iranian oil, the Strait of Hormuz will definitely be closed," Mohammad Kossari, deputy head of parliament's foreign affairs and national security committee, told the semi-official Fars News Agency.