NEW YORK - The U.N. Security Council authorized Thursday an expanded political mission in Afghanistan to strengthen support for the Afghan government as the country confronts increasing insurgent violence.

The resolution was approved unanimously by the 15-member council.

"Afghanistan is one of the most important issues facing the world, because the struggle against terrorism and against extremism in that part of the world is the defining challenge of our time," U.S. Ambassador Zalmay Khalilzad said.

Renewing the mandate for another year gives the mission and Kai Eide of Norway, the new U.N. special representative in Afghanistan, responsibility for providing "more coherent support by the international community to the Afghan government" and for leading the U.N. in "a strengthened and expanded presence throughout the country."

Last week, the U.N. peacekeeping chief called for a U.N. "course correction" in Afghanistan to improve coordination of international civilian efforts to help promote peace.

Undersecretary-General for Peacekeeping Jean-Marie Guehenno told the council the international community has been committed and generous, but all too often "insufficiently united."

The council first established the U.N. mission in Afghanistan in 2002. It provides technical help, political and strategic advice and other support for the Afghan government, while also promoting human rights and managing aid for people struggling to rebuild their lives.

Italian Ambassador Marcello Spatafora said the mission was "sharpened" to improve coordination with international civilian and military efforts, based on Secretary-General Ban Ki-moon's recommendation.

"Once again the council is rallying strong and united behind one of the most important U.N. missions," Spatafora said.

The council's resolution expresses concern about "increased violent and terrorist activities by the Taliban, al-Qaida, illegally armed groups, criminals and those involved in the narcotics trade, and the increasingly strong links between terrorism activities and illicit drugs."

Insurgent violence in Afghanistan is at its highest level since U.S. forces invaded the country in 2001 to oust the hard-line Islamic Taliban rulers, who harbored al-Qaida leaders blamed for planning the terrorist attacks in the United States on Sept. 11, 2001.

Approval of the resolution coincided an unannounced visit Thursday to Afghanistan by Vice President Dick Cheney. The vice president stood beside Afghan President Hamid Karzai and told reporters the United States will call on NATO countries to do more to help with Afghanistan's recovery from years of strife.

Karzai has told the U.N. that he supports its efforts to help Afghans, particularly those who feel "alienated" from government but support its laws.