U.S. President George W. Bush said Friday that global efforts are needed to prevent the spread of weapons of mass destruction (WMD), as members of the Proliferation Security Initiative (PSI) gathered here for a meeting.

In a letter to the conference, Bush, the launcher of the initiative, said: "I commend all member nations for their readiness to take on this vital task and I urge all responsible states to join this global effort to end the WMD proliferation threat."

"The PSI is dedicated to stopping all aspects of the proliferation trade, and denying terrorists, rogue states and their supplier networks access to WMD-related materials and delivery systems," he said in the letter read by Under Secretary of State for Arms Control Bob Joseph who heads the U.S. delegation.

The PSI was initiated by Bush during his tour of Poland in 2003 to form an international network against the spread of WMDs.

Polish President Lech Kaczynksi, who was also absent from the meeting, sent a message saying the PSI "will efficiently contribute to the fight against terrorism and the countries pursuing nuclear programs without any consultations and against the will of the international community."

Delegations from about 70 countries attended the meeting to review progress and discuss the future steps.

The final statement of the conference said the proliferation of WMDs and terrorism was "one of the gravest dangers to the global community" and demanded "constant vigilance."