ACCORDING TO a recent story in The Post, the Obama administration is “quietly toasting” the success of international sanctions against Iran. The Islamic republic is having increasing difficulty arranging imports, including food, and the central bank is reportedly short of hard currency. Billions of dollars in foreign investment projects have been canceled, and few banks, insurance companies or shipping firms are willing to do business with Tehran.

There are also signs of political stress. President Mahmoud Ahmadinejad is bitterly at odds with conservative clergy and a majority of parliament and appears to have lost the support of Supreme Leader Ayatollah Ali Khamenei. Iran’s closest ally, the Syrian regime of Bashar al-Assad, is slowly but steadily losing ground to a popular uprising, raising the prospect that Iran’s once-firm foothold in the Arab Middle East will be reduced to an isolated Hezbollah militia in Lebanon.

We don’t begrudge the White House a toast or two over these developments; the administration has worked hard and relatively effectively to make the sanctions work. But it’s important to note a stubborn reality: There has been no change in Iran’s drive for nuclear weapons or in its aggressive efforts to drive the United States out of the Middle East.

If anything, Tehran has recently grown bolder. Last month it announced plans to triple its capacity to produce uranium enriched to the level of 20 percent — a far higher degree of processing than is needed to produce nuclear energy. Western diplomats and experts say that Iran is preparing, and may have already begun, to install a new generation of powerful centrifuges in a plant built into a mountain near the city of Qom. As British Foreign Secretary William Hague wrote in an op-ed published by the Guardian last week, it would take only two to three months to convert the uranium enriched at Qom into weapons-grade material. That means that Iran could have a “breakout” capacity allowing it to quickly produce a weapon when it chose to do so.

Mr. Hague told the British Parliament last month that Iran also has been secretly testing medium-range missiles capable of carrying a nuclear warhead. Britain believes there have been three such tests since October. Meanwhile, Iranian-backed militias have launched a new offensive against U.S. forces in Iraq. According to Defense Secretary Leon Panetta and other senior officials, Tehran has supplied sophisticated rockets and roadside bombs for attacks on U.S. troops, 15 of whom were killed during June.

Iran’s ability to sustain its nuclear program and its meddling in Iraq reflect the fact that these initiatives are controlled by the Revolutionary Guard, which has not been affected by the political feuding in Tehran and has first claim on the oil revenue that Iran continues to reap. Economic and political hardship also has had no apparent impact on Mr. Khamenei, who has maintained the regime’s refusal even to negotiate with the U.N. Security Council, much less obey its resolutions.

The bottom line is that the threat from Iran is not diminishing but growing. Where is the policy to reverse that alarming trend?