The top United Nations envoy in Afghanistan, Staffan de Mistura, told the U.N. Security Council Wednesday the war-torn country is at a crossroad as it begins to take on responsibility for its own security.

De Mistura said that Afghanistan's transition must not be just about security, but must also be linked to social and economic conditions, and to human rights. Doing so will help ensure that the transition becomes “solidly irreversible,” he said, adding that the U.N. will do its part towards that end.

Afghanistan's U.N. representative Zahir Tanin said his country is at a “critical juncture.” He said Taliban militants are trying to incite fear among Afghans and hamper international support for Afghanistan, as well as undermine the peace talks and the prospect of reconciliation.

Tanin added that the Afghan government is also committed to resolving the controversy over last year's parliamentary elections after a special court set up by President Hamid Karzai overturned the results for 62 of the parliament's 249 seats because of alleged fraud.

U.S. Ambassador to the U.N. Susan Rice said Washington is cooperating with Afghan and international partners on the election controversy and urged Afghan political leaders and institutions to act in accordance with the Afghan constitution and electoral law.

Earlier Wednesday, U.N. Secretary-General Ban Ki-moon appointed Britain's Michael Keating as his new deputy special representative for Afghanistan.

The U.N. mission in Afghanistan said Keating brings extensive experience in managing humanitarian emergencies and post-conflict recovery programs in Afghanistan, the Middle East and Africa.

Keating replaces Robert Watkins of Canada, who has been appointed to be the deputy special coordinator for Lebanon.

Keating was born in Uganda and has spent 15 years working for the United Nations.

He will also serve as the U.N.'s humanitarian coordinator in Afghanistan.