Governments supplying them with weapons were undermining their own credibility as defenders of international law and human rights as well as the credibility of the international system, she said.
“It sends a message that these rules apply differently to us and our allies as they do to others, and that has really serious consequences,” she said.
This contradiction when Western countries were demanding accountability for Russia’s invasion of Ukraine was being exploited by countries like Russia and China, she said.
“They are very quick to point out double standards from the West and are trying to use that to undermine the system.”
Hassan spoke to Reuters as the UN rights office released a report on the death toll in the Israel-Hamas Gaza war where it said nearly 70 per cent of verified fatalities were women and children.
Palestinian authorities say that more than 43,500 people have been killed in Gaza in the 13-month war triggered by Hamas attacks on southern Israel on Oct 7, 2023, in which 1,200 people were killed and 250 taken hostage.
“This should now motivate the world into action. There is really no justification for the killing of children,” Hassan said.
On Oct 13, Washington imposed a deadline for its ally Israel to improve the humanitarian crisis in Gaza or face potential restrictions on US military aid.
Asked about the likely impact of the election of Donald Trump in the United States, she said there was “little assurance” of his commitment to international law during his previous tenure as president.
“Now we have seen in some of the statements on the campaign trail threats of mass deportation of millions of people and this sends a very worrying message,” she added.