KABUL, Afghanistan - The United States and Afghanistan plan to expand the Afghan army by up to 12,000 soldiers and to accelerate shipments of of U.S. M-16 rifles, armored humvees, and other weaponry by the spring to counter a growing threat from Taliban insurgents and al-Qaeda fighters, U.S. and Afghan commanders said yesterday.

South of Kabul today, a suicide bomber rammed his explosives-laden car into a minibus full of Afghan soldiers, killing at least 12 people and injuring seven, officials and witnesses said.

Gen. Mohammad Zahir Azimi, a defense ministry spokesman, said six soldiers and six civilians were killed and seven soldiers were injured.

The blast was the third suicide attack in the city in the last eight days.

Under the new military plan, the Afghan army would then begin recruiting as many as 12,000 additional soldiers, for a total of 82,000, according to Lt. Gen. Sher Mohammed Karimi, the army's operations chief. The army, now 50,000 strong, expects to reach its target strength of 70,000 soldiers by mid-2008, Afghan and U.S. officials say.

While U.S. officials cite the achievements of the Afghan military, the force has historically suffered from high attrition rates. It has also lacked sufficient military aid and trainers and has been hobbled by old weaponry, Afghan defense officials say.

During a visit to Afghanistan yesterday, Defense Secretary Robert M. Gates was met at every stop with urgent requests - from Afghan generals, U.S. commanders and tribal leaders - for more U.S. funding, troops, military equipment, and even an airfield and a hospital.

Appearing with Gates, President Hamid Karzai made a broad public appeal for increased assistance. "If you are asking me whether we need more, I will never say no. I will keep asking for more," he said at a packed news conference at his presidential palace in Kabul.

This year has seen the highest overall level of violence in Afghanistan since the U.S. military led a campaign in late 2001 to oust the Taliban government, with unprecedented casualties among U.S. and other coalition troops, Afghan forces, and civilians.

Suicide bombings and cross-border strikes have increased, and more foreign fighters affiliated with al-Qaeda are infiltrating Afghanistan, according to Western and Afghan officials.

Gates, voicing concern about a growing level of violence, said one reason for the increased fighting was "a much more aggressive effort" by coalition troops to move into Taliban sanctuaries.

The Pentagon is considering a series of initiatives to counter Taliban and al-Qaeda offensives. In addition to expanding the Afghan army, officials are looking at ways to build local police forces and improve governance to help communities resist incursions by insurgents.

The Associated Press contributed to this article.