John Bolton, the top US diplomat for arms control, said Canada, Denmark, Norway and Singapore would participate in the next meeting of countries involved in the so-called Proliferation Security Initiative.
Military and law enforcement experts from those countries will join officials from Australia, Britain, France, Germany, Italy, Japan, the Netherlands, Poland, Portugal, Spain and the United States at that meeting which is set to be held in the United States later this month, he said.
Some 50 nations have expressed interest in joining the group which is examining ways to intercept nuclear, chemical and biological weapons on the high seas or in international airspace.
"As the PSI moves forward, we expect other countries will join in training exercises to enhance global capabilities to respond quickly when governments receive intelligence on proliferation shipments," Bolton said.
Since US President George W. Bush proposed the initiative earlier his year in Poland, PSI backers have held four military exercises simulating seizures of WMD from ships and aircraft.
Six others such exercised are planned at various locations up to next spring.
At the US-hosted meeting this month, the experts "will analyze their authorities against real world scenarios and examine any gaps in authorities that can be filled either through national legislation or policy or international action," Bolton said.
They will also be looking at ways to improve law enforcement and military cooperation and information sharing, he said.