There's a reason few people write letters anymore. In a world of BlackBerrys, e-mail, cell phones and fax machines, the old-fashioned letter is simply too slow to deliver important information.

Unless, of course, your intention is to send a message to someone other than the person to whom the letter is actually addressed.

That's why lawmakers often issue open letters to the president. If they really wanted to influence him, they'd call the White House. But when they want to use the media to influence us, they send off a letter encouraging the president to do something.

This probably explains the recent missive from Iran's mercurial president Mahmoud Ahmadinejad. He proposes "new solutions for getting out of international problems and the current fragile situation of the world."

But it's not actually aimed at President Bush. His real intention is to influence public opinion. He doesn't actually want to open a dialogue with the United States. Ahmadinejad's simply stalling for time so Iran can finish building its nuclear weapons program.

Frighteningly, they're quickly closing in on their goal, and the international community isn't doing much to interfere. In March the United Nations Security Council urged Iran to suspend its uranium-enrichment activities and fully cooperate with the International Atomic Energy Agency. But the IAEA admitted on April 28 that Iran has ignored that warning.

In fact, the Iranian government has repeatedly violated the 1968 Nuclear Nonproliferation Treaty and has made clear that it intends to keep right on doing so until it has the bomb. When faced with the threat of U.N. Security Council sanctions, Ahmadinejad was refreshingly clear. Iran "won't give a damn about such useless resolutions," he announced.

It's time for the United States to act.

As a first step, we should demand that the U.N. Security Council impose targeted diplomatic and economic sanctions on Iran unless it immediately freezes its nuclear research and allows international access to its facilities. These inspections must be allowed "anytime, anywhere," to preclude Iranian cheating.

Russia and China probably will block these measures, as they have so far blocked any Security Council action. If that happens, the United States should push ahead by leading a coalition of the willing to impose sanctions outside the U.N. framework. And we certainly won't be alone.

Our longtime ally Britain likely would join the effort. Iran is a growing threat, and as Prime Minister Tony Blair said last October: "If they carry on like this, the question people will be asking us is -- when are you going to do something about Iran? Can you imagine a state like that, with an attitude like that, having nuclear weapons?"

At the same time, Washington should make it clear that if Iran presses ahead with its nuclear research, the United States will invoke its right to self-defense under Article 51 of the United Nations Charter.

There's little doubt that Israel and the United States would be the top targets of a nuclear Iran. After all, Ahmadinejad himself has announced that, "God willing, with the force of God behind it, we shall soon experience a world without the United States and Zionism," and he's called for Israel to be "wiped out from the map." Even if the United Nations won't take such threats seriously, the United States and our democratic allies must.

Iran's president is using old-fashioned methods to get his message across, and the United States should answer in kind. We should use Ahmadinejad's letters to try to determine what he'll do next. But we should also make clear -- to Iran and the U.N. -- that the United States isn't going to allow Iran to go nuclear. It's time to remind our enemies we're ready, willing and able to act in our own defense.

Edwin Feulner is president of The Heritage Foundation (heritage.org), a Washington-based public policy research institute and co-author of the new book Getting America Right.