CHARIKAR, Afghanistan?An American bomb blasted huge plumes of smoke 1,000 feet into the skies over Afghanistan’s front lines Tuesday in an unusually mighty airstrike. The Pentagon said U.S. forces were with the northern opposition and directing fire against the Taliban.

The opposition alliance deployed hundreds of crack troops near Taliban lines north of Kabul, the first tangible sign of preparations for an assault on the capital.

The United States acknowledged it had uniformed military personnel in Afghanistan, coordinating airstrikes with the opposition. A senior opposition official said such coordination will increase in coming days and that alliance forces were planning a major offensive to wrest the strategic northern city of Mazar-e-Sharif from the Taliban.

“There is coordination in all aspects,” Abdullah, the foreign minister of the Afghan government-in-exile, said in an interview with Associated Press Television News.

U.S. jets pounded Taliban positions in the Balkh region around Mazar-e-Sharif on Tuesday, in strikes that an opposition spokesman called relentless.

“They hit very important positions of the Taliban,” spokesman Ashraf Nadeem said.

Witnesses also said they saw a U.S. plane drop a bomb Tuesday at the Bagram front lines, about 25 miles north of Kabul, creating a mushroom cloud that billowed at least 1,000 feet into the air. Witnesses called it the biggest bomb to hit the area in 10 days of American bombardments on the front lines.

Despite the U.S. aerial attacks, the opposition alliance has made no advances against the ruling militia. The opposition has complained the U.S. strikes were not intense enough.

The United States launched the air campaign on Oct. 7, aiming to punish the Taliban regime for refusing to hand over Osama bin Laden, whose al Qaeda terror network is blamed for the Sept. 11 attacks in the United States.

At the Pentagon, Defense Secretary Donald Rumsfeld said American forces were “very aggressively” going after Taliban defenses facing the opposition and that 80 percent of the strikes Tuesday had been slated to target the front lines.

He said a “very modest” number of uniformed military personnel were on the ground in the north coordinating with the opposition on supplies and targeting and giving information “helpful to the air effort.” But Rumsfeld underlined that the opposition planned its offensives independently.

American jets bombed near the fronts north of Kabul and Mazar-e-Sharif on Tuesday, as well as the cities of Jalalabad in the east and Kandahar in the south, according to Taliban and other reports.

“There were a lot of planes,” said Hadi Abdul Khalq, an Afghan refugee who said he fled Kandahar on Tuesday, and who spoke on the Afghan side of the border near Chaman, Pakistan. “The people were very scared and they were rushing in all directions. We can’t take any more.”

Jets also rained bombs on a front line northeast of Taloqan, another northern city that the opposition hopes to wrest from Taliban control.

“We are very happy to see the military system of the Taliban hit by the bombs and to see their system paralyzed,” said Saeed Jaffar, an opposition spokesman in the area.

Near the front lines north of Kabul, the opposition was deploying a corps of some 800 to 1,000 elite troops, well armed, trained and ready for the order to march on the capital.

“We are ready for action,” said 25-year-old Ahmad Zai, toting a Kalashnikov rifle and a rocket launcher. He said he expected to move on Kabul “in the near future.”