MOSCOW, May 31: Russia cast aside its doubts on Monday and joined a US-led alliance of countries prepared to board ships and raid suspect factories in a crackdown against weapons of mass destruction.

Moscow said it had become the 15th core member of U.S. President George W. Bush's Proliferation Security Initiative (PSI), designed to stop such arms ending up in states viewed with distrust by Washington, such as North Korea and Iran.

"The threat of proliferation of weapons of mass destruction is global and accordingly requires a global response," the Foreign Ministry said in a statement. "We are sure that we can cope with the problem only through a collective effort."

Russia, which basically supports stopping any illegal trade in nuclear, chemical and biological weapons-related materials and missiles, initially had strong reservations about Bush's initiative, put forward a year ago.

Russian experts expressed fears a right to intercept suspicious vessels could give a legal role of global policeman to the United States, which has the strongest naval presence across the world.

Another concern was the PSI could be used to hamper Russia's commercial interests because it trades with many countries at odds with Washington, such as Iran or Syria.

Russia announced its decision a week before a summit of the Group of Eight major industrial nations at Sea Island, Georgia, where the PSI is going to be high on the agenda. Russia was the last G8 member to join the initiative.

U.S. officials have said Russia joining the PSI would have extra political importance because it could inspire another major power, China, to become a core member.

Russian officials had said after talks with US Under secretary of State John Bolton in Moscow earlier this month that Russia still had some unanswered questions. The foreign ministry said Russia would contribute to the PSI as long as its actions did not violate the law. -Reuters