The diplomat who was president of the UN Security Council in April 1994 apologized Wednesday for the council's refusal to recognize that genocide was taking place in Rwanda and for doing nothing to halt the slaughter of more than one million people.

Former New Zealand ambassador Colin Keating issued the rare apology during a council meeting to commemorate the 20th anniversary of the genocide and examine what has been done since to prevent new genocides.

The open session elicited praise for the UN's stepped-up commitment to put human rights at the centre of its work but widespread criticism of its failure to prevent ongoing atrocities in Syria, Central African Republic and South Sudan.

The council unanimously adopted a resolution calling on all countries "to recommit to prevent and fight against genocide" and reaffirming their responsibility to protect people from crimes against humanity. It condemned any denial of the Rwanda genocide and underscored the importance of taking into account lessons learned from the slaughter of Tutsis and moderate Hutus.

Keating recalled that New Zealand, Nigeria, the Czech Republic and Spain, supported by Argentina and Djibouti, urged condemnation of the Rwanda genocide in April 1994, the month it started, and called for reinforcement of the UN mission in the country, but "most" veto-wielding permanent members objected. The United States and France were among those opposed.

U.S. Ambassador Samantha Power acknowledged that the United States supported extracting UN troops rather than reinforcing them, which could have saved thousands of lives.

She cited lessons learned, including the establishment of a UN special adviser on the prevention of genocide, courts to prosecute alleged perpetrators, and UN efforts that helped end or deter violence in East Timor, Liberia, Sierra Leone, Libya, Kenya and Ivory Coast.

"Overall, however, it is both fair and profoundly unsatisfying to admit that our successes have been partial and the crimes against humanity that persist are devastating," Power said. "Too often, we have done too little, waited too long, or been caught unprepared by events that should not have surprised us. Moving forward, we have to do a better job of confronting and defeating the practitioners of hate."

Keating said the UN Secretariat concealed "a critical piece of advice" -- a cable from force commander, Gen. Romeo Dallaire that "gave graphic early warning of a probable genocide." He said the Geneva-based Human Rights Commission warning of the likelihood of genocide was never brought to the council's attention.

"All this confirms that there are many lessons about information, about early warning and about how to use information, which I believe are still relevant today," Keating said.

Rwanda's UN Ambassador Eugene-Richard Gasana said "the systematic slaughter of men, women and children was perpetrated in full view of the international community."

"The genocide against the Tutsi highlighted the extent to which the UN methods of prevention utterly failed," he said.

Gasana said the "horrific" scenes from Central African Republic, Syria and South Sudan today have convinced many people that the UN still has a long way to go on the issue.

UN Deputy Secretary-General Jan Eliasson said those conflicts "sadly show that the protection of populations from atrocities remains lagging and elusive."

At a UN commemoration Wednesday evening, Secretary-General Ban Ki-moon, the Rwandan and U.S. ambassadors and other representatives lit candles in memory of the victims of the genocide. Dozens of people attending the ceremony then stood for a minute in silent tribute.

"We have pledged never again, again and again but this world is still divided," Ban said. "The ongoing challenges in South Sudan, Syria and Central African Republic show that we have much work ahead of us."

Jordan's UN Ambassador Prince Zeid al Hussein asked his fellow council members, particularly the permanent members, whether they had learned anything from the Rwanda genocide, and what words they would use that would be "immune to the inevitable mockery, the cynical laughter" of the people of the Central African Republic whose relatives have been killed in unprecedented fighting between Muslims and Christians.

While the Security Council authorized a UN peacekeeping force for Central African Republic last week, Zeid said the time lag in finding and deploying troops, and the financial constraints are similar to the way the UN confronted crises in 1994.

"And ultimately, are we not too late -- again?" he asked. "We all care, yes, maybe. But it is equally clear we still do not care enough; not enough to act immediately, overwhelmingly, in those cases where an intervention is needed."