HANOI, May 22. /ITAR-TASS/. Vietnam has joined the Proliferation Security Initiative (PSI), Vietnamese Foreign Ministry spokesman Le Hai Binh said on Thursday.

Over 100 countries backed the US-led PSI, a multinational response to the challenge posed by the threat of the proliferation of weapons of mass destruction (WMD), their delivery systems and related materials.

Russia joined it in 2004.

The goal of PSI is pre-emptive interdiction, which includes detaining and searching ships and aircraft as soon as they enter PSI members' territorial waters or national airspace; denying suspicious aircraft over- flight rights; grounding planes when they stop to refuel in member countries or in states willing to cooperate on a case-by-case basis; and boarding and searching ships registered in a PSI member nation or operating under a flag of convenience of another state prepared to authorize an interdiction in a particular instance.