Washington ? Spare parts for Iraq’s military are being smuggled from eastern Europe and former Soviet republics, keeping Saddam Hussein’s troops prepared for combat despite an international embargo on weapons trafficking, U.S. defense officials say.

The equipment from truck tires to aircraft parts is being brought across the border from Syria and Jordan in trucks, officials believe. They commented on condition of anonymity.

Iraq uses many of the same Warsaw Pact-era tanks and planes as eastern Europe and the former republics of the Soviet Union. But it’s unclear who is getting the equipment into the country, and U.S. officials do not accuse any of the governments where the material originated.

The equipment may come from arms traffickers and corrupt military personnel in the former Soviet bloc, officials said. Iraq is able to purchase the parts with profits from oil smuggled into Jordan and elsewhere.

Officials are unable to specify how much equipment is reaching the Iraqi army and air force. Sometimes U.S. officials learn that certain kinds of prohibited equipment have reached Baghdad only when they observe, say, previously grounded aircraft taking to the skies for pilot training.

The U.N. embargo, in place since the Iraqi invasion of Kuwait in 1990, has stopped Iraq from importing complete weapons systems like combat aircraft or tanks, officials said. But it is able to maintain some of its aging arsenal with the smuggled spare parts.

The parts also allow for more training for Iraq’s military, which numbers more than 400,000 troops according to official estimates. That’s 40 percent of the million-man army Saddam boasted before the 1991 Gulf War.

The Iraqi military is spread around the country to oppose rebel groups, Iran and the possibility of a U.S. attack from the south. Its main purpose is to keep Saddam in command, U.S. officials say.

Iraq would be no pushover for the United States, experts say. Unlike the Gulf War, some Iraqi troops would regard a U.S. attack as an invasion and fight harder to defend their homeland, said Ivo Daalder of the Brookings Institution in Washington.

“It’s not that we won’t win” if the United States does take military action, Daalder said. “But it doesn’t necessarily have to be easy. It depends on how quickly the enemy is going to collapse.”