If anyone doubts the extremism of Iran, that doubt should be erased by Iran's threat to choke off one-sixth of the world's oil supplies by closing a strategic Persian Gulf waterway, the Strait of Hormuz.

The strait leads from the Persian Gulf -- which borders oil-rich Saudi Arabia -- to the Arabian Sea and the Indian Ocean. Iran is on one side of the strait. The United Arab Emirates is on the other. About 15 million barrels of oil pass through the Strait of Hormuz every day, supplying much of the world's oil needs.

Iran threatened to close the strait in response to possible sanctions by the United States -- sanctions being considered because of Iran's alarming attempts to develop nuclear weapons.

Iran's actions almost instantly started driving up gasoline prices in the United States, and our country warned Iran against carrying through with its threat.

We do not doubt the ability of the U.S. Navy to keep the strait open -- by force if it comes to that.

But this latest crisis highlights some important facts:

• First, Iran is ruled by radicals with whom ordinary diplomatic negotiations are fruitless. That already should have been evident from Iran's support for terrorists, and it is reason to take very seriously Iran's efforts to obtain nukes and its repeated vows to destroy Israel.

• Second, Washington should stop hiding behind flimsy environmental excuses for refusing to develop our country's oil and natural gas supplies. We rely on unstable Middle Eastern and South American regimes for much of our oil. But do we honestly think those nations are more likely than the United States to have meaningful environmental safeguards in place? If we developed more of our own energy, we would not be affected so severely by the threat of a shutoff of foreign supplies.

The time to take seriously the threat that Iran poses -- and the time to unleash our nation's energy potential -- is now.