GENEVA - The United States accused Iraq, North Korea and four other countries yesterday of building germ-warfare arsenals and said it is worried one of them might be helping Osama bin Laden in his quest for biological weapons.

"We are concerned that (bin Laden) could have been trying to acquire a rudimentary biological weapons capability, possibly with support from a state," said John R. Bolton, undersecretary of state for arms control.

The existence of Iraq's program is "beyond dispute," he said, while stopping short of making a direct linkage to bin Laden.

Nor did he say whether any of the five other countries he cited as being at various stages of germ-warfare development - Libya, Syria, Iran and Sudan as well as North Korea - are suspected of trying to supply bin Laden.

Bolton spoke at the start of a three-week conference to review 1972 Biological Weapons Convention, which has been ratified by 144 countries.

Iraq immediately rejected the allegation it was violating the global ban on germ warfare and said the United States was making the claim as a pretext for an attack on Baghdad.

On Sunday, Condoleezza Rice, President Bush's national security adviser, left open the possibility that Iraq could become a target in Bush's war on terrorism.

"We do not need the events of September 11 to tell us that (Saddam Hussein) is a very dangerous man who is a threat to his own people, a threat to the region and a threat to us because he is determined to acquire weapons of mass destruction," she said.

Anthrax-tainted letters that have led to the deaths of four people in the United States have focused attention on the threat of biological warfare.

Bolton said U.S. officials had yet to determine the source of the anthrax attacks but noted that bin Laden has said he wanted to obtain weapons of mass destruction and use them against the United States.

"We are concerned that he could have been trying to acquire a rudimentary biological weapons capability, possibly with support from a state," Bolton said.

But he said the United States was "not prepared, at this time, to comment whether rogue states may have assisted" bin Laden, who is suspected of organizing the Sept. 11 attacks.

Bolton told reporters "an unfortunate number" of countries are violating the treaty and have operational biological weapons programs.

After careful consideration, the United States had decided to name only six and would "be contacting privately" the others, he said.

As well as Iraq, North Korea has an "extremely disturbing" biological weapons program, Bolton said.

North Korea could likely "produce sufficient quantities of biological agents for military purposes within weeks of a decision to do so," he said.

The United States also is "quite concerned" about Syria, Iran, Libya and Sudan, Bolton said.

Iran's ambassador to the conference, Ali Asghar Soltanieh, called the U.S. allegations "baseless." The United States made the accusations to sow discord into attempts to strengthen the treaty, he said.

Libya also denied having a biological weapons program.

Last summer, the United States shocked other treaty countries by rejecting six years of negotiations on a verification system to strengthen the 1972 treaty.

Bolton said the proposed enforcement mechanism, described in a 210-page document, was "hopelessly defective" and would not be resurrected.

Washington says the system would fail to stop bioterrorism, could expose weaknesses in U.S. biodefense plans, would not prevent countries from obtaining "dual use" technology that could be applied to making biological weapons and could reveal legitimate commercial secrets of U.S. pharmaceutical companies.

The United States has the world's largest biotech industry.

Bolton said U.S. officials would rather set up a mechanism under which the U.N. secretary-general would order inspections when violations are suspected.

He said it was a "fact of life" if that meant the United States and four other Security Council countries with veto power could keep themselves from being inspected.

However, other countries, including Japan and the 15-nation European Union, said a binding commitment would be necessary if the treaty is to be effective.

Chinese Ambassador Sha Zukang said strengthening the treaty was "one of the most effective ways to combat" bioterrorism.

Bolton said a better approach would be if each country adopted national legislation to make violations of the treaty a criminal offense. Individuals accused of such violations should be subject to extradition to other countries, he said.