Updated: Feb. 5, 6:46 p.m.

Just how seriously does the Obama administration take the threat of Iran’s nuclear program? It’s hard to tell.

[IMGCAP(1)]In his 71-minute State of the Union address last week, President Barack Obama devoted just five lines to what may emerge as the top foreign policy issue of 2010.

“The international community is more united, and the Islamic Republic of Iran is more isolated,” he said.

“And, as Iran’s leaders continue to ignore their obligations, there should be no doubt: They will face growing consequences. That is a promise.”

The good news comes with the word “as.” It replaces the previous “if,” indicating that Obama has finally concluded that diplomacy is failing to stop Iran’s work on a bomb and that it’s time to move to “consequences.”

Secretary of State Hillary Rodham Clinton said last April that the administration would seek international agreement on “crippling sanctions” against Iran. But the process is going to be slow and there’s reason to doubt that the Iranian regime really will be crippled.

Congress, to its credit, is far ahead of the administration. In December, the House passed, 412-12, the Iran Refined Petroleum Sanctions Act, authorizing steps to cut off Iran’s imports of gasoline.

Last week, the Senate passed a similar bill on a voice vote with no dissent. Though Iran is oil-rich, it lacks refining capacity and has to import 40 percent of its gasoline. When the government moved to ration gas in 2006, riots ensued.

In a speech Jan. 24, House Foreign Affairs Chairman Howard Berman (D-Calif.), chief sponsor of the House measure, declared that “in my view, there is no greater threat to the world than the prospect of a nuclear Iran.”

You don’t hear that kind of talk from the administration — and, according to Rep. Mark Kirk (R-Ill.), original sponsor of the gasoline-cutoff legislation in 2006, the administration seems reluctant to impose any sanctions that might adversely affect the Iranian people.

Adm. Dennis Blair, the administration’s director of national intelligence, buried Iran deep in his annual worldwide threat assessment this week.

And he pointedly did not reverse a 2007 National Intelligence Estimate — reportedly disputed by both foreign and U.S. intelligence agencies — that Iran stopped its nuclear weaponization program in 2003.

“We continue to assess [that] Iran is keeping open the option to develop nuclear weapons in part by developing various nuclear capabilities that bring it closer to being able to produce such weapons, should it choose to do so,” he told the Senate Intelligence Committee. “We do not know, however, if Iran will eventually decide to build nuclear weapons.”

As all the world knows, Iran has been secretly enriching uranium, defying international demands that it stop, building missiles capable of carrying warheads and threatening the existence of Israel.

According to some press reports, it is also working on a sophisticated nuclear detonation system.

The Obama administration set a deadline for the end of last year for Iran to respond to its diplomatic “outreach.” The deadline passed a month ago.

The next step is to seek tougher sanctions at the United Nations Security Council this month. But that’s almost certain to fail because China will veto them.

Iranian President Mahmoud Ahmadinejad just gave China a perfect excuse to do so by saying he sees “no problem” with agreeing to a proposal to ship uranium out of the country for reprocessing.

Iran previously has rejected that idea. Hinting it might accept it is clearly designed to ward off sanctions and play for time.

The next step, if the administration is serious, would be to form a “coalition of the willing” with Europe to impose tough economic sanctions.

One talked-of action is an international economic boycott of entities connected with the Iran Revolutionary Guard Corps, the powerful political-military-clerical conglomerate that now controls the country, including much of its energy and nuclear program.

Another is isolation of Iran’s central bank from international commerce, which could collapse of the value of Iran’s currency.

On its own, the United States could enforce the 1996 Iran Sanctions Act, which calls for exclusion from U.S. business of any company in the world doing more than $20 million worth of business with Iran’s energy sector.

No penalties have ever been imposed under the law — despite the fact that Iran just signed a $1.4 billion natural gas deal with an unnamed German firm. That firm was widely believed to be Siemens AG, although Siemens CEO Peter Loescher issue the following statement Friday: “The Siemens board decided at the start of October not to agree to any further orders with customers in Iran.”

As for any current business arrangements, Siemens announced last week it would stop doing business with Iran — but not until the middle of this year.

And, of course, the administration could start working on a “regime change” — overtly and covertly assisting the “Green movement” protesting the brutal rule of Ahmadinejad and Supreme Leader Ali Khamenei.

According to Berman, “unfortunately, there are no sanctions that are both strong enough to dissuade the Iranian regime from its nuclear course and limited enough not to impinge on the quality-of-life of average Iranians. …

“Sanctions that hurt the Iranian economy will impose painful nukes-or-butter choices on a regime that is already tottering. Sanctions could be lifted once the regime complies with U.N. Security Council resolutions demanding that it suspend uranium enrichment.”

Kirk told me that he favors “the whole ball of wax” — enforcement of the Iran Sanctions Act, isolation of IRGC entities and Bank Markazi — and a cutoff of Iran’s gasoline imports.

The cutoff would be executed, he said, by buying up insurance contracts on ships transporting fuel to Iran — then canceling them.

Ships still bringing in gasoline would be “quarantined” in international waters, which he said would not constitute a naval blockade of Iran, an act of war.

“The point of sanctions is to be effective,” he said. “The Iranian people are already demonstrating against their government.

“If you’re going to attack the central bank and collapse the currency, you’re going to hurt the Iranian people. And if you cut off gasoline supplies you send the economy into a spiral.

“Of course you will get protests against President Obama for a couple of weeks because the regime will organize them. But as factories close and refrigerators become empty, the people would begin to blame their own government.”

This well may be the Year of Iran. If the world can’t stop its nuclear program with sanctions, Israel might try to do so with bombs.