US President George W. Bush said the US would stop North Korea from transferring nuclear weapons to Iran or al-Qaeda and that the communist regime would then face "a grave consequence."
Bush refused to spell out how the US would retaliate.
"They'd be held to account," the president said in an ABC News interview on Wednesday.
In light of North Korea's Oct. 9 nuclear test, Bush warned that any transfer of nuclear material elsewhere in the world by the North would be considered a grave threat to the security of the US.
Bush previously used "grave threat" in relation to Iraq's former president Saddam Hussein, whose government was toppled in the US-led war in 2003.
"If we get intelligence that they're about to transfer a nuclear weapon, we would stop the transfer, and we would deal with the ships that were taking the -- or the airplane that was dealing with taking the material to somebody," he said.
Asked how he would retaliate, Bush would not be specific.
"You know, I'd just say it's a grave consequence," he said.
Bush said the North Korean leader should "understand that he'll be held to account."
"Just like he's being held to account now for having run a test," Bush said.
The US repeatedly has said it does not intend to attack the North, but it also has refused to take any military option completely off the table.