Despite urgent U.S. pleas, Russian companies are continuing to provide Iran with technology for weapons of mass destruction, a senior administration official said Wednesday.

The technology could help Iran in its programs to develop chemical, biological and especially nuclear weapons, the official said.

By contrast, he said, Russian President Vladimir Putin is trying hard to persuade North Korean leader Kim Jong Il to abandon or at least curtail his program to develop long-range missiles.

The Russians do not agree with the Bush administration that North Korea will be able to mount a long-range threat. They say North Korea is patterning its program on shorter-range Russian Scud missiles.

But, the official said, the Bush administration has advised the Kremlin that tests show the program can be adapted to pose a long-range threat and Russia does not deny there is a North Korean missile problem.

Speaking to reporters at the State Department on condition of anonymity, the official said the technology sales to Iran are a sore spot in generally improved U.S. relations with the Russian government, which, he said, is aware of the deals.

Officially, Russia agrees with the United States that curbs should be placed on proliferation of technology to Iran. But the Bush administration has not made much progress in persuading Russian authorities to clamp down, the official said.

Still, the administration persists, telling Russian officials that an Iran armed with weapons of mass destruction poses a threat to Russia as well, the official said.

On another troubled front, Russia has not given up its attempt to crush secession in Chechnya with force, the official said.

The United States ambassador to Moscow, Alexander Vershbow, plans to make a trip to the troubled republic to signal U.S. concern.