Afghan President Hamid Karzai says his country is embarking on a “long journey to self-reliance.”

Speaking Sunday at a donors conference in Tokyo, Mr. Karzai said Afghanistan is facing “years of hard work” as international troops stationed in the South Asian nation initiate their exit.

Donor nations Sunday pledged $16 billion in aid to the war-torn country over the next four years.

Senior world officials are in attendance at the conference, including U.S. Secretary of State Hillary Clinton, who has offered assurance the United States will not abandon the Afghan people after U.S. combat troops leave the country in 2014.

“We must ensure that the transition is irreversible and that Afghanistan can never again be a safe haven for international terrorism.”

President Karzai said while Afghanistan has taken an important stride towards democratization with a new constitution, the country still faces a major threat to its security.

“Afghanistan continues to face grave risks from common threats, notably terrorism and extremism. These threats do not affect Afghanistan's security alone. Indeed, the region as a whole, and the world beyond, will not be secure for as long as the menaces of terrorism and extremism persist, enjoying sanctuaries and support in some corners of the region beyond Afghanistan's borders.”

Mr. Karzai said corruption in Afghanistan has undermined previous aid efforts and promised to do more to bring it under control.

“Corruption in particular is a menace that has undermined the effectiveness, cohesion and legitimacy of our institutions. We will fight corruption with strong resolve wherever it occurs, and ask the same of our international partners. Together we must stop the practices that feed corruption or undermine the legitimacy and effectiveness of national institutions.”

U.N. Secretary General Ban Ki-moon said Afghanistan stands at a critical point in its history as it prepares for a transition to a more stable future. He said Afghanistan need strong support through its transition.

“But let us be clear. Transition must not translate into short-term measures only. We should give the people of Afghanistan a long-term perspective and prospect of a better future, and ease their worries that Afghanistan may be abandoned.”

Mr. Ban told the conference international donors should make their assistance reliable and predictable, without unreasonable conditions.

“At the same time, it is of course Afghanistan itself that bears the primary responsibility to live up to its obligations to better serve its people in line with the commitments made in Bonn, Kabul and London.”

Before the conference started, Clinton announced that Washington has declared Afghanistan a major non-NATO ally, a step that will allow Afghanistan to receive more and faster help on security matters.