In the late 1990s , UN-authorised international interventions took a wider variety of forms . The UN mission in the 1991 – 2002 Sierra Leone Civil War was supplemented by British Royal Marines , and the UN-authorised 2001 invasion of Afghanistan was overseen by NATO . In 2003 , the US invaded Iraq despite failing to pass a UN Security Council resolution for authorization , prompting a new round of questioning of the organization 's effectiveness . In the same decade , the Security Council intervened with peacekeepers in crises including the War in Darfur in Sudan and the Kivu conflict in the Democratic Republic of Congo . In 2013 , an internal review of UN actions in the final battles of the Sri Lankan Civil War in 2009 concluded that the organization had suffered " systemic failure " . In November/December 2014 , Egypt presented a motion proposing an expansion of the NPT ( non-Proliferation Treaty ) , to include Israel and Iran ; this proposal was due to increasing hostilities and destruction in the Middle-East connected to the Syrian Conflict as well as others . All members of the Security Council are signatory to the NPT , and all are nuclear weapons states
the final battles
Alleged war crimes during the final stages of the Sri Lankan Civil War
United Nations Security Council