FOR SOME TIME President Bush has been promising to change the long-standing U.S. practice of cultivating dictators in strategically important parts of the world in exchange for their support on security issues or reliable supplies of oil. This week his administration took a significant step in that direction -- and in a region where it could have an important impact. The State Department announced that $18 million in military and economic aid to Uzbekistan, a Muslim country in Central Asia, would be suspended because of its failure to carry out a promised political liberalization or improve its human rights record. Driven in part by congressional pressure, the cutoff should send a message to Uzbekistan's authoritarian president, Islam Karimov, as well as several of his neighbors in a region where oil, gas and military bases have recently become important: The old formula for partnership with Washington may no longer work.

Mr. Karimov, who ruled Uzbekistan when it was still a Soviet republic, has appeared eager to imitate the Arab autocrats who have enjoyed U.S. funding or protection while suppressing their own people. Soon after Sept. 11, 2001, he allowed the Pentagon to establish an air base near his capital, with more than 1,000 personnel, for operations in neighboring Afghanistan. He visited Washington in 2002 to propose a "strategic partnership" with the Bush administration and pretended to be planning sweeping democratic reforms. Mr. Karimov even signed a memorandum spelling out his pledges -- and then returned to jailing and torturing his political opponents, censoring the media and staging fraudulent elections. He had reason to believe his cynical tactics would work. After all, Egyptian President Hosni Mubarak has played by a similar script for years and reaped tens of billions of dollars in U.S. aid.

Uzbekistan's relationship with the United States is still evolving, however, as are those of several Muslim neighbors whose authoritarian rulers have sought to win U.S. sanction with military favors or oil concessions. Last year Congress passed legislation to hold Mr. Karimov to his word: Unless the administration certified progress on the reforms he had promised, both economic and military aid would be withheld. After several public warnings and months of hesitation, Secretary of State Colin L. Powell finally ruled that certification was impossible. A State Department statement said that "this decision does not mean that either our interests in the region or our desire for continued cooperation with Uzbekistan has changed" but that "progress in democratization, respect for human rights and economic reforms are essential for Uzbekistan's security and long-term prosperity, as well as to reinforce a solid and enduring relationship with the United States." Maybe Mr. Karimov won't listen. But it is very likely that many people in Uzbekistan and around the region will take note -- and be encouraged to draw new conclusions about the priorities of the United States.