BBC News with Julie Candler

The international envoy to Syria Kofi Annan is to

quit

his role as mediator on behalf of the United Nations and the Arab League at the end of the month. Mr Annan said the increasing militarization in Syria and a clear lack of unity at the UN Security Council fundamentally changed the effectiveness of the role he'd undertaken. Imogen Foulkes reports.

When Kofi Annan was first appointed, many within the United Nations and the Arab League were optimistic that he was the man to bring peace to Syria. Mr Annan enjoys a great deal of trust – not only in Washington and Moscow, but crucially in the Middle East itself. But as the weeks and months moved on, and not one of the six points on his plan were implemented, Mr Annan grew frustrated. In his resignation speech, he made it clear he felt the trust in him had never led to a genuine commitment to peace.

The United States said Mr Annan's mission could never have succeeded as long as the Assad government continuously broke pledges to implement his peace plan. The US ambassador to the United Nations, Susan Rice, said that by a

blocking

action at the Security Council, Russia and China had made his mission impossible. The Russian President Vladimir Putin said he regretted Mr Annan's resignation and called him a brilliant diplomat.

US media says President Obama authorized covert to American support for Syrian opposition forces earlier this year. It's been rumored for some time that the CIA has been assisting Syrian rebels from Turkey. Kim Ghattas has more.