GENEVA-Human rights are under assault worldwide, the United Nations chief warned on Monday, citing widespread abuses of international law and devastating civilian suffering in conflicts in Sudan, Gaza, and Ukraine.

"The rule of law is being outmuscled by the rule of force," said U.N. Secretary General Antonio Guterres, speaking at the opening of the Human Rights Council in Geneva.

Human rights are being pushed back deliberately, Guterres said, urging member states not to view international human rights as a menu to pick from.

Guterres strongly defended the U.N. human rights system which is in "survival mode" because of funding cuts, attacks on some of its experts and the United States' withdrawal from one of its key universal rights accountability mechanisms.

"Humanitarian needs are exploding while funding collapses," he said.

The U.N. human rights office, like other parts of the organisation, faces a budget crunch following the decision to cut funding by the United States - the top donor to the U.N. - as well as other governments.

Washington in February paid about $160 million of the more than $4 billion it owes to the U.N., a United Nations spokesperson said on Thursday.