WASHINGTON — The United States faces a cold reality: even stepped-up U.S. and Western sanctions of recent weeks have not persuaded Iran’s radical regime, which is driving ever closer to nuclear weaponry, to shift course.

WASHINGTON, D.C. — The Iranian plot to assassinate the Saudi ambassador to the United States and bomb Saudi and Israeli embassies in Washington and elsewhere was not some bizarre move by a rogue operator within Iran’s government.

It was, instead, the logical next step in Iran’s increasingly lethal war against the United States — a step demanding that Washington discard its all-too-predictable calls for greater international “isolation” for Tehran, and its reticence for confrontation, by responding with military action.

Make no mistake: U.N. Security Council sanctions and additional U.S. and European pressures are hurting Iran.

Tehran is having a harder time importing food and other key goods, its foreign investment is drying up, financial firms and shipping companies are turning down its business, and its central bank is running short of hard currency.

An Army psychiatrist at Fort Hood, Texas, allegedly kills 13 of his service mates. A Pakistani immigrant tries to set off a car bomb in Times Square. An American convert to Islam murders a military recruiter in Arkansas.

Each reportedly subscribed to a radical strain of Islam that, they believed, directed them to defend their faith by killing Americans. These attacks, along with the dozens of home-grown plots we know about, raise obvious questions about dangers that may be emanating from the American Muslim community of 2 million to 3 million people.