bulgaria's eu association agreement came into effect in 1994, and bulgaria formally applied for full eu membership in december 1995. during the 1999 eu summit in helsinki, the country was invited to start membership talks with the union. on january 1, 2007 bulgaria officially became a member of the european union. in 1996, bulgaria acceded to the wassenaar arrangement controlling exports of weapons and sensitive technology to countries of concern and also was admitted to the world trade organization. bulgaria is a member of the zangger committee and the nuclear suppliers group. after a period of equivocation under a socialist government, in march 1997 a udf-led caretaker cabinet applied for full nato membership, which became a reality in april 2004.