The Group of Eight leading industrial democracies have urged North Korea and Iran to curb their nuclear programmes and branded weapons of mass destruction (WMD) the leading threat to world stability.
A statement issued at a summit in France, G8 leaders said the spread of nuclear, biological and chemical weapons and their delivery means, along with terrorism, was "the pre-eminent threat to international security".
The world community had to use arms inspections, export controls "and if necessary other measures in accordance with international law" to tackle the threat, the declaration said in an oblique reference to the possible use of force.
It made no reference to the US-led war in Iraq, launched on the premise that Iraq possessed yet-to-be-discovered banned arms but which half of the G8 countries opposed.
"We strongly urge North Korea to visibly, verifiably and irreversibly dismantle any nuclear weapons programmes," it said.
"We will not ignore the proliferation implications of Iran's advanced nuclear programme," it added, appealing to Tehran to comply with its obligations under the Non-Proliferation Treaty and accept more intrusive UN inspections without conditions.
However, US President George W. Bush reassured G8 leaders that the United States had no intention of attacking Iran, Italian Prime Minister Silvio Berlusconi said.
He told a news conference after G8 leaders discussed thepossibility that Tehran might be developing nuclear weapons:"Bush made a clear statement that the idea of an armed operation by American forces in Iran is completely without foundation."
Iran recently acknowledged it had a far more extensive nuclear research programme - including uranium enrichment - than previously declared. But it denies seeking atomic arms.
The Group - the United States, France, Germany, Britain, Italy, Canada, Russia and Japan - agreed on a plan to keep radioactive material from falling into the hands of terrorists. It would entail tighter monitoring of the location of materials and confining export to states "that have effective controls".
The G8, which includes the world's main manufacturers of shoulder-fired missiles, urged all nations to do more to ensure terrorists could not get hold of portable anti-aircraft weapons.
The leaders pledged still tighter export controls to ensure WMD technology was not passed on irresponsibly.
Since last year's G8 summit in Canada, "events in the world have underscored the relevance of those principles and the urgency of implementing them," the statement said.
US Deputy Defense Secretary Paul Wolfowitz said that Washington had imperfect intelligence about communist North Korea's nuclear capability, but took seriously Pyongyang's assertions it has atomic bombs.
Washington has also piled pressure on Tehran, accusing it of seeking nuclear weapons, backing international terrorism and undermining Middle East peace efforts. It also alleges Tehran is interfering in efforts to rebuild neighbouring Iraq.