Washington: The Obama administration, seeking to build on the momentum of the Iran resolution passed last week by the United Nations, announced on June 16 that it had imposed sanctions on more than a dozen Iranian companies and individuals with links to the country's nuclear and missile programs.
The list includes two top commanders of the Islamic Revolutionary Guards Corps, which has control over Iran's nuclear program and is expanding its grip on the nation's economy.
It also includes a major Iranian bank and five front companies for the Iranian state shipping line, as well as 71 ships with names that had been changed to skirt previous sanctions.
"Iran will never cease looking for ways to evade our sanctions," Treasury Secretary Timothy F. Geithner said in announcing the measures at the White House. "So our effort must be ongoing and unrelenting. And we will keep working on ways to intensify financial pressure on Iran."
Administration officials said they hoped the steps would be the first of a new round of sanctions against Iran by the European Union, Australia and other countries.
On Thursday, European leaders are expected to endorse their own unilateral measures, while Congress is drafting legislation that would go much further than the United Nations sanctions.
But the Treasury Department's sanctions lay bare the loopholes that continue to plague efforts to isolate Iran commercially: many of the companies on the list acted as fronts for entities already the subject of previous sanctions. Others have ties to entities that were already sanctioned.
Moreover, a senior administration official acknowledged that the United States would have had the authority to designate all these companies on its own without the passage of the latest United Nations resolution. The sanctions require that the companies' assets under American jurisdiction be frozen.
The administration's move came hours after a defiant speech by Iran's president, Mahmoud Ahmadinejad, who said the West deserved to be punished for its action against Tehran and laid out ambitious plans to increase uranium enrichment and build four new atomic research facilities.
Iran justified the need to expand enrichment to supply fuel for a research reactor that produces radioactive isotopes. It plans to build the research complexes in four corners of the country and said that one of them would be "more powerful" than the American-built research reactor in Tehran, which has been the subject of intense negotiations among Iran, Western nations, Brazil and Turkey.
"You showed bad temper, reneged on your promise, and again resorted to devilish manners," Mr. Ahmadinejad said, addressing the countries that voted to pass the resolution in the United Nations Security Council.
"You have behaved badly," Mr. Ahmadinejad said, "but we have terms which will punish you and make you sit at the negotiating table like a polite child."
He also said in the speech, which was broadcast live on state television, that Iran would announce new conditions for talks, suggesting that he was open to dialogue in the wake of the Security Council vote.
The administration met these mixed signals with sanctions that aimed to show how Iran used its banks and shipping industry to aid its nuclear program.
The United States designated Post Bank of Iran, which American officials said handled foreign transactions for Bank Sepah after it was penalized in 2007 for providing financing to Iran's missile industry.
Also named were five companies -- two based in Hong Kong -- that are affiliated with, or owned by, the Islamic Republic of Iran Shipping Lines. Iran has evaded previous sanctions by renaming, repainting and reflagging its ships.
It also has changed the ownership of the vessels, officials said.
The administration kept its focus on the Islamic Revolutionary Guards Corps, designating the corps' air force and missile command, which it says have links to Iran's ballistic missile program. And it named two top commanders: Mohammad Ali Jafari, the commander in chief of the corps since late 2007, and Mohammad Reza Naqdi, who has served as head of the Basij Resistance Force since October 2009 and was notorious earlier for suppressing protests at Iranian universities.
Basij paramilitaries led the government's bloody crackdown on antigovernment protests after the disputed presidential election last June, though that is not the main reason that Mr. Naqdi was sanctioned.
As a former deputy chief of staff of the armed forces general staff, he was involved in efforts to evade previous sanctions, according to the United Nations.
The Treasury Department also identified 22 companies in the Iranian insurance, petroleum and petrochemical industries that it said were owned by the Iranian government.
American citizens are barred from doing business with such companies; the designations are also devised as a warning to foreign companies with business dealings in Iran, officials said.
Some critics said the sanctions, particularly those against well-established figures like Mr. Jafari, showed how hard it was for the United States to keep up with the Islamic Revolutionary Guards Corps. The Revolutionary Guards "is morphing, and expanding, and drifting into every part of the Iranian private sector every day," said Danielle Pletka, a vice president and an expert on Iran at the American Enterprise Institute. "We have a handful of people in Treasury who do this, and we're not keeping up."