U.S. President George Bush says there will be grave consequences for North Korea if it tries to export nuclear weapons. The United States and Japan say they will work together to enforce U.N. sanctions against North Korea.
President Bush says he will use all means necessary to hold North Korea to account if it attempts to transfer nuclear weapons.
"If we get intelligence that they are about to transfer a nuclear weapon, we would stop the transfer. We would deal with the ships that were taking or the airplane that was dealing with taking the material to somebody," he said.
In an interview with the American television network ABC, President Bush said North Korean leader Kim Jung Il should understand that the United States is serious about preventing Pyongyang from sharing nuclear technology.
"I want the leader of North Korea to understand that he will be held to account, just like he is being held to account now for having run a test," he said.
Last week's nuclear test by North Korea brought United Nations sanctions against the country. Russia and China had previously resisted such a move. Asked if China was now fully committed to enforcing those sanctions, President Bush said he is confident that Beijing shares the goal of a nuclear-free Korean peninsula.
"They don't particularly want to board ships, but on the other hand, if there is good intelligence, they will work with us on that intelligence. They are inspecting cargo that is coming across their border," he said.
President Bush says he does not know if those sanctions will work but he says he knows the international community must try.
North Korea's nuclear test has become an issue in next month's U.S. congressional elections.
Some Republicans say former Democratic President Bill Clinton failed to address that threat and instead enabled North Korea by agreeing to economic incentives in 1994 in exchange for a promise to stop developing nuclear weapons that Pyongyang broke.
Opposition Democrats say North Korea's nuclear advances show that President Bush has focused too much on the war in Iraq and not enough on North Korea and Iran.
A public opinion poll by the television network CNN says 72 percent of Americans believe the war in Iraq makes it harder to deal with North Korea.
U.S. Secretary of State Condoleezza Rice is in the region to consult with allies.
She says Washington is not trying to escalate the crisis but the U.N. Security Council has acted firmly and resolutely to say that North Korea's nuclear test is unacceptable.
North Korea says the sanctions are a declaration of war.