Supporters say UN mediation has prevented even worse outcomes, but security council is stuck in vicious circle

• Middle East crisis – latest news updates

As diplomats from nearly 200 member states gather in New York this week for the United Nations general assembly against the backdrop of a massive Israeli bombing campaign in southern Lebanon, a nagging question to be addressed is whether the UN is too broken to be fixed.

UN officials are facing three intractable conflicts, in the Middle East, Ukraine and Sudan. While it remains one of the most important humanitarian organisations on Earth, organising relief efforts for refugees, natural disaster victims and others in dire need, the UN’s principal security body appears to be powerless to intervene in some of the world’s most grinding conflicts.