London ? Iraq poses an increasing threat that must be met, the defense chiefs of the United States and Britain said Wednesday, showing growing impatience with Saddam Hussein.

“We know that Saddam Hussein’s regime in Iraq has had a sizable appetite for weapons of mass destruction” and is finding ways to acquire the ingredients, Defense Secretary Donald H. Rumsfeld said.

“We know the borders into that country are quite porous,” he added, allowing Iraq to import technologies with applications in both civilian and military industries as well as illicit materials.

“There is not a doubt in the world that with every month that goes by, their programs mature,” he said.

Iraq denies it has or is developing any weapons of mass destruction, but it has refused to allow the international inspections that it agreed to accept as a condition of ending the 1991 Gulf War.

Rumsfeld would not discuss the possibility of U.S. military action to topple Saddam’s government, saying that was a matter for President Bush to decide. He spoke at a joint news conference with British Defense Secretary Geoff Hoon after meetings to discuss Iraq and other issues.

For months the Bush administration has been publicly making the case for taking strong action possibly military against Iraq, but allied nations have been slow to offer support.

Wednesday in Washington, Senate Majority Leader Tom Daschle of South Dakota said his fellow Democrats support a push to unseat Saddam. “The question is when and how and under what circumstances,” Daschle said.

A day earlier, House Democratic leader Dick Gephardt volunteered his support if the administration resorted to force. “I share President Bush’s resolve to confront this menace head-on,” he said.

Also on Tuesday, Bush said that “one option, of course, is the military option.” The president added, however, he had no plans to attack.

Hoon described the Iraqi military threat as increasing in recent weeks. Asked in a later interview to elaborate, Hoon said Iraq’s air defenses were more aggressively trying to shoot down the U.S. and British pilots who regularly fly combat air patrols over northern and southern Iraq.

Pilots have reported attacks in recent week by Iraqi anti-aircraft artillery and surface-to-air missiles. The allied planes have responded by bombing various elements of Iraq’s air defense system.

Since the start of U.S. and British enforcement of the “no-fly” zones more than a decade ago, Iraq has considered them a violation of its sovereignty and has vowed to shoot down planes.

The recent aggressiveness would suggest a new, more worrisome Iraqi attitude, Hoon said.

“Clearly they are feeling a little more confident than they have in the recent past,” he said.