* More than 60,000 dead in Syria's 21-month conflict
* Both sides accused of committing atrocities
* Security Council unlikely to refer Syria to ICC
More than 50 countries asked the U.N. Security Council on Monday to refer the Syria crisis to the International Criminal Court, which prosecutes people for genocide and war crimes, in order to send a signal to Syrian authorities.
More than 60,000 people have been killed during a 21-month-old revolt against Syrian President Bashar al-Assad, which began with peaceful protests but turned violent after Assad's forces cracked down on demonstrators.
Both sides have been accused of committing atrocities, but the United Nations says the government and its allies have been more culpable. U.N. rights chief Navi Pillay has also called for Syria to be referred to the International Criminal Court.
"We are firmly of the view that the Security Council must ensure accountability for the crimes that seem to have been and continue to be committed in the Syrian Arab Republic and send a clear signal to the Syrian authorities," read the letter sent by Switzerland on behalf of more than 50 states.
"The situation on the ground has only become more desperate, with attacks on the civilian population and the commission of atrocities having almost become the norm," read the letter, supported by permanent council members France and Britain.
The United States, China and Russia, the other three permanent council members, are not members of the ICC.
World powers are divided over how to stop the escalating violence in Syria and the 15-member council is unlikely to refer the situation in Syria to the International Criminal Court in The Hague - which is not an official U.N. body.
Permanent Security Council members Russia and China have acted as Syria's protector on the council by repeatedly blocking Western efforts to take stronger U.N. action - such as imposing sanctions - against the Syrian government to try to end the war.
"At the very least, the council should send out an unequivocal message urging the Syrian authorities and all other parties to fully respect international human rights and humanitarian law in the ongoing conflict," read the letter.
The letter said the council should announce "that it intends to refer the situation to the ICC unless a credible, fair and independent accountability process is being established in a timely manner."
Syria is not a party to the Rome Statute, which set up the International Criminal Court, so the only way the court can investigate the situation is if it receives a referral from the Security Council. The council has previously referred conflicts in Libya and Darfur, Sudan to the court.
International peace envoy Lakhdar Brahimi has unsuccessfully tried to get Russia and the United States to agree on how to end the violence in Syria.
Brahimi has said the main sticking point was the issue of Assad. The United States, European powers and Gulf-led Arab states insist he must step down to end the war, but Russia has said Assad's exit cannot be a precondition for a peace deal.
Brahimi's predecessor, former U.N. Secretary-General Kofi Annan, warned on Monday that if no political proposals were put forward then a stalemate could be created. Annan had blamed the Security Council impasse for hampering his six-month bid to broker peace and leading to his decision to step down. ž
"Those who are saying mediation is a waste of time have offered no alternative, they are hoping for intervention, but I haven't seen any countries lining up to intervene," Annan told reporters. "You have a situation where you have a sectarian war coming up and Syria can explode beyond its borders."