In his first speech to the United Nations Prime Minister Stephen Harper asked for more help in Afghanistan, describing the conflict as a test of the world body's relevance.

Harper said Canada understands the task is difficult and a challenging road lies ahead before success is achieved in Afghanistan, but he also said the future of the United Nations depends on success in the country.

If the countries of the world fail to respond to Afghanistan's request for help from the UN, they will be failing themselves, Harper said.

He described the work in Afghanistan as a mission "where global interest and higher purpose come directly together," and challenged the UN to do more to address the key requirements of reconstruction and security.

"The success of this mission in providing both security and development is vital to the safety, livelihood and very future of the Afghan people. But it is also vital to the health and future of this organization," Harper said.

"This is the United Nations' strongest mission and therefore our greatest test. Our collective will and credibility are being judged. We cannot afford to fail. We will succeed."

• Full text of speech

Harper also challenged the pace of change at the UN and said it needs to become more accountable -- pointing to his own government's steps to improve accountability as a good example for the body to follow.

Harper also briefly touched on other major challenges facing the UN, including conflicts affecting Haiti, Darfur and Lebanon, and suggested that the time for getting tough with Iran over its nuclear ambitions is getting close.

Opposition responds

Liberal foreign affairs critic Keith Martin spoke to reporters shortly after Harper's speech. He said the prime minister failed to address three key areas of the mission despite the fact he "devoted an inordinate amount of time to that mission" in his speech.

Martin said Harper focused on the military aspect -- which he acknowledged is crucial to success -- but virtually ignored development efforts, the need to develop a plan to end the insurgency, and the training of Afghan security forces to eventually take over from foreign troops.

Martin also criticized Harper for failing to mention the spread of AIDS in Africa and the ongoing civil war in the Darfur region of Sudan, where Martin said international troops are desperatelty needed.

"We wanted the prime minister to stand up at the United Nations and have a ... cry of the heart, to call on the international community and the United Nations to get those boots on the ground so lives can be saved, civilians protected and aid can get through."

NDP Leader Jack Layton was also harshly critical of Harper's speech.

"According to government documents Canada is spending $141 dollars on combat for every man, woman and child in Afghanistan, and only $16 per person on aid and reconstruction," Layton said Thursday during question period in the House of Commons.

"Today we see the prime minister at the United Nations asking the world to help with reconstruction in Afghanistan even though we're spending eight, nine times more on war than we are on aid. Why doesn't the prime minister start to put some balance into his own approach?"

The prime minister's speech appeared to be tailored for a domestic audience as well as an international one as critics at home claim the mission is costing too much.

Since 2002, 36 Canadian soldiers and one diplomat have died in Afghanistan. Canada currently has 2,200 soldiers in the country.

NATO recently appealed for allied governments to provide up to 2,500 extra troops to help in the fight against Taliban forces across southern Afghanistan.

Currently, there are about 20,000 UN-sanctioned troops in Afghanistan, mostly taking part in peacekeeping and rebuilding in the north and west.

Canada's has 2,200 troops who are fighting alongside British, Dutch and U.S. soldiers as they push south through Taliban territory.

The NDP wants the troops withdrawn, and the Bloc Quebecois has demanded an emergency parliamentary debate on the issue.

Harper set the stage for his UN speech with a Wednesday night address to the powerful Economic Club of New York. In that speech, Harper touted Canada's oil resources and called on members to persuade the U.S. Congress to hold off on a strict new identification plan for those seeking to cross the border, saying the move threatens the close relationship between Canada and the U.S.

With a report from CTV's Graham Richardson