Administration officials told The New York Times that the exercises — which were to involve practice of "nonpermissive boarding" of ships" — were meant as a signal to North Korea to end its pursuit of nuclear weapons.
Officials from the United States, Australia, Japan and eight European countries — agreed in principle last month to begin training for high seas "interdictions" of ships believed to be carrying weapons of mass destruction. The European countries are Britain, France, Germany, Italy, the Netherlands, Poland, Portugal and Spain.
While officials here have not named any nations that would be targeted by such raids, North Korea is thought to be high on the list.
"We are not saying which countries are being targeted, because it would not be politically wise," an Asian diplomat told The Times. "But the American government believes that one of the reasons why North Korea has agreed to the six-party talks in Beijing is that they are feeling the pinch."
No date has been given for the first exercises next month in the Coral Sea off Australia's northeast coast.
"The government is considering using the maritime component of the routine bilateral Exercise Crocodile 03 scheduled for September in the Coral Sea as a potential opportunity to conduct this type of training," the Australian Defense Department said in a statement, referring to the possible maritime interdictions.
The exercises will come shortly after officials from North and South Korea, the United States, China, Japan and Russia meet for Aug. 27-29 talks in Beijing to discuss Pyongyang's nuclear program.
North Korea has been locked in a nuclear dispute with the United States and regional countries since October, when it claimed to have started a program to turn uranium into nuclear fuel. The U.S. stopped fuel shipments, and North Korea kicked out international inspectors and vowed to begin reprocessing fuel rods into weapons-grade plutonium.
North Korea has refused to allow international inspectors to return to the country to monitor its nuclear program and has demanded that the United States commit to a nonaggression treaty and a normalization of relations.
Meeting China's leaders Monday in Beijing, Australian Prime Minister John Howard said, "The North Korean nuclear threat is about as real and serious a threat as we can have anywhere in either the region or the world."
If employed, the ship-boarding tactics would be both to prevent North Korea from importing material for its nuclear program and shipping weapons overseas.
Earlier this year, a North Korean freighter suspected of carrying heroin was boarded off the East Coast of Australia by elite troops who rappelled from helicopters after it refused repeated demands by pursuing Australian Navy ships to stop.
The ship's crew was arrested and charged with smuggling heroin. While no firm link has been established between the ship and North Korean authorities, it is believed that Pyongyang exports illicit drugs to prop up its failing economy.
On Dec. 9, Spain's navy, working with U.S. authorities, intercepted a North Korean ship carrying missiles to Yemen, but the cargo was released after Yemen protested.
Officials tell The Times that as in the case of the shipment to Yemen, international law may pose an obstacle to efforts to stop ships on the high seas. Article 89 of the United Nations Convention on the Law of the Sea states: "No State may validly purport to subject any part of the high seas to its sovereignty."
But The Times reports that barrier could be breached with either a new United Nations sanctions regime or a strategy of stopping ships for the ostensible purpose of investigating some violation of maritime law, but for the real purpose of searching the cargo for weapons.
On Monday, South Korea's navy fired warning shots after a North Korean fishing boat entered waters controlled by the South, the military said.
The North Korean ship turned back and there was no further hostility between the two sides, South Korea's Office of Joint Chiefs of Staff said in a statement.
The fishing boat intruded 594 feet into southern waters along the disputed western sea border, the statement said. South Korean navy speedboats fired five warning shots and the Northern boat returned to communist territory five minutes later.
The maritime border between the two Koreas is not clearly marked, and North Korean fishing boats often cross over into South Korean waters. South Korean navy ships occasionally respond with warning shots.
South Korea is studying whether Monday's alleged violation was intentional. The navies of the two Koreas, which were divided in 1945, fought deadly skirmishes in the western sea in 1999 and 2002.