American bombers are hitting hard inside Iraq, getting a head start toward disabling Saddam Hussein's defenses in the south, while other U.S. forces are on the ground in the north preparing for war.

U.S. and British warplanes bombed three dozen sites in January, most associated with air defense communications in the southeast. That's the route invading U.S. ground troops probably would take if war should come. The Pentagon also has acknowledged it has inserted a small number of troops into the north, although it refuses to describe their mission.

Meanwhile, pilots have nearly doubled the supplies of leaflets dropped over the south to undermine the rule of Iraqi President Saddam, to 3 million this month.

"We're kind of getting a head start," Lexington Institute military analyst Loren Thompson said, speaking of the increasing airstrikes. "We're taking advantage of the situation to reduce Iraqi defenses so we can use the full weight of our air power when the war does come."

The situation he speaks of is the dominance the allies have over a large portion of Iraq's skies. For more than a decade, the U.S.-British coalition has enforced flight-interdiction zones over the north and south in the name of keeping Iraqi forces from harassing Kurdish and Shiite Muslim populations in those regions.

Patrols over the zones have benefited the coalition by facilitating the gathering of intelligence, getting practice in dealing with Iraqi forces and becoming familiar with the territory.

On Wednesday, 11 of the 15 U.N. Security Council members advocated more weapons inspections and peaceful disarmament of Iraq rather than a rush to war. But a Bush administration impatient with Saddam has steadily continued the deployment to the region of tens of thousands of troops for a possible military campaign.

Inside Iraq, meanwhile, the Defense Department has accelerated bombing and dropping propaganda in the decade-old southern flight-interdiction zone. It also has sent the troops into the north, where the CIA has been checking out airstrips and working with opposition groups.

Degrading air defenses in southern Iraq helps clear the way for sending in not only U.S. bombers but helicopters, special operations forces and materiel for the campaign, Thompson said.

Officials say pilots in the U.S.-British coalition strike only in response to Iraqi activity. Thus, increased bombings in recent months result from an increase in such Iraqi actions as firings on coalition planes or flying Iraqi planes into the zone, they say.

Much of the increase in coalition strikes this month, however, owes to the bombing by coalition pilots of as many as eight locations for a single Iraqi action.

Pilots go out with lists of predetermined targets, parts of the air defense system officers want destroyed. Last fall they would hit one or perhaps two targets in response to Iraqi gunners. But of the 12 days in which coalition pilots have bombed so far this month, half have seen pilots bombing three, four, five or eight sites on the basis of one Iraqi move.

Most of the multiple sites targeted were cable repeater sites, stations built at intervals along a fiber-optic cable network to strengthen signals passing through the network.

This cable system, which connects elements of the air defense system, helps Iraqi defenders process a larger volume of communications data and better protect data against eavesdropping by American electronic warfare planes, officials said. It was one of the reasons U.S. and British aircraft conducted a larger-scale attack in February 2001, although their success was limited in part because more than half the bombs missed their mark. A few months after the attack, Iraq had largely reconstituted the network, and the United States protested to China, which officials have said was helping Iraqis build the system.

This month, coalition planes targeted cable repeaters frequently in the southeast, five times near Al Kut, four near An Nasiriyah and twice near Basra, the country's main port, according to U.S. Central Command press releases put out after each mission.

Because the command now refuses to say whether it hits or misses targets in the zones, it was impossible to learn whether pilots flying the repeat strikes were going after missed targets or hitting new targets near the same towns.

Defense officials also have said that pilots frequently have to go back and strike the same areas because Iraqis constantly rebuild or replace what is damaged.

"A lot of it is not terribly sophisticated," Anthony Cordesman of the Center for Strategic and International Studies said of parts of the air defenses. He said Iraqis have learned to buy multiple supplies of things to keep replacing what is bombed.

Officials differ on the extent of damage that has been done to the air defense system, with one saying it's been severe, another less effective than that and still another that it has damaged the morale of those who must rebuild it more than the system itself.

From time to time, strikes have focused on wearing down other important Iraqi targets. A spate of bombings in September and October focused on Tallil Air Base, a facility key to Saddam's defense against any invasion. It's also in the south.