Asian and Western members of the UN Human Rights Council failed to find a common voice on the situation in Sri Lanka before they were due to hold a special session on the issue on Tuesday.
Switzerland, with the support of about 30 mainly Western states, has tabled a draft resolution calling on Colombo to "investigate all allegations" of human rights abuses during Asia's longest-running civil war between the Sri Lanka army and the rebel Tamil Tigers.
It also called on the Sri Lankan government to ensure the freedom of displaced people and access to drinking water and sanitation.
However, another draft text tabled by countries including China, India, Pakistan and Sri Lanka "commends" Colombo's actions in dealing with internally displaced people, and encouraged UN agencies to continue cooperating with the Sri Lankan government.
Sri Lanka's allies did not mention any possible probe.
The 47-state Human Rights Council, which was formed in 2006 to react more quickly to emergency situations, is meeting more than two months after UN human rights chief Navi Pillay spoke about possible "war crimes and crimes against humanity" committed by both sides.