The United States says it will spearhead a campaign to promote competitive elections for the United Nations Human Rights Council to keep violators from winning seats as part of a new effort to reform the world body.
Joseph Torsella, US ambassador for UN management and reform, said members of the organisation's top human rights body should be held to the same standard it promotes around the world.
"Abusers of international law or norms should not be the public face of the UN," he said.
The proposed reforms come as the US presidential campaign heats up. Many of the UN's operations, its resolutions criticising Israel, and the membership of the Human Rights Council have come under attack from some Republicans, especially Ileana Ros-Lehtinen, who chairs the House of Representatives' Foreign Relations Commission.
Currently, elections to the Human Rights Council and many other UN bodies are controlled by regional groups which often put forward uncontested slates.
In 2010, seven countries accused of human rights violations, including Libya, Angola and Malaysia, won seats on the Human Rights Council in uncontested elections.
Last year Syria was a candidate for an uncontested Asian seat, but it withdrew after the US and the European Union lobbied UN members against voting Yes for a country that was cracking down on civilian protesters.
In a speech to the Council on Foreign Relations in Washington, sent to UN correspondents, Mr Torsella said the US also planned to take action against countries that broke international law elsewhere in the UN system.
"If a member state is under Security Council sanction for weapons proliferation or massive human rights abuses, it should be barred, plain and simple, from leadership roles like chairmanships in UN bodies," he said.
Mr Torsella said the size and scope of the UN had grown dramatically since the world body was established in 1945, but that the UN "is still, in too many ways, stuck around 1950". While the UN's regular two-year operating budget for 2010-2011 ended at £3.5 billion, he said, when all the agencies in the UN system were included it was now a £23.2 billion enterprise - larger than the individual GDPs of half its 193 member states, he said.