U.S. forces launched a new assault on caves and potential hide-outs in the mountains of southern Afghanistan early today after intelligence reports suggested high-ranking members of al Qaeda and the Taliban could be in the area, U.S. officials said.

About 600 U.S. troops were participating in the operation in the remote, arid region -- the third major operation in the area in the past two months.

U.S. officials declined to say whether al Qaeda leader Osama bin Laden is among the targets of the operation, but a Pentagon official in Washington said intelligence indicates al Qaeda and Taliban fighters in the area of the operation have communications equipment, considerable firepower and some degree of organization. That means there could be leadership elements in the cave complexes being searched.

"We're trying to get the leadership," the official said. "Somebody's going to tie us in and tell us where they are." The official also said that while the operation is similar to attacks over the past two months, "you're pulling a whole lot of forces into a concentrated area."

The offensive consisted of an early morning assault by troops ferried in by helicopter and a ground convoy to the Sami Ghar mountains 100 miles east of Kandahar, according to a military spokesman, Col. Roger King.

There were no reports tonight of combat or casualties among U.S. troops or rebel fighters, King said.

In Washington, Defense Secretary Donald H. Rumsfeld and Air Force Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, said the assault was not timed to coincide with the war with Iraq or meant to counter critics who say the Iraqi campaign will divert military attention from the war on terrorism.

But, Rumsfeld added, the attack on Iraq "isn't taking anything away from the war against al Qaeda."

The attack was focused in the Maruf district of Kandahar province, according to Khalid Pashtun, a spokesman for the Kandahar provincial government. U.S. forces and their Afghan allies had suspicions about activities in at least three different villages in the mountainous region, where inhabitants have tribal links to the former leader of the Taliban, Mohammad Omar.

The troops involved are elements of Special Forces and the 82nd Airborne Division's 504th Parachute Infantry Regiment, known as the White Devils, King said. The soldiers were airlifted by helicopter into the region and deployed to surround the suspected militants. Additional support staff was to arrive by truck convoy.

Among the sources of information the military was acting on, King said, was the interception of radio transmissions, possibly from caves in the Sami Ghar mountains. He said that attacking and clearing the caves was a key part of the mission.

The commander of coalition troops in Afghanistan, Lt. Gen. Dan K. McNeill, said last week that he was planning a busy spring, with assaults in many areas of southern and eastern Afghanistan. Afghan rebels historically have mounted their own campaigns in the spring, and the increased activity by coalition troops is an effort to disrupt their plans and ability to regroup.

Since late January, coalition forces, which number about 11,000 in Afghanistan, have also staged assaults in the area north of Spin Boldak, in Kandahar province, and in the Baghran Valley in Helmand province. Those efforts involved hundreds of soldiers and significant firepower. Both operations lasted several weeks but resulted in relatively few militants being captured or killed, although the military called them successful because they cleared enemy fighters from strongholds.

There has been an increasing number of attacks on Afghan government posts in the southern portion of the country in recent weeks. Authorities generally blamed the activity on remnants of al Qaeda, the Taliban and followers of Gulbuddin Hekmatyar, a militant commander recently labeled as a terrorist by the United States. All of those remnants are believed to have crossed the border and to be living in relative safety in the tribal areas of Pakistan, which are under limited government control.

On Wednesday, militants ambushed an Afghan government post in southern Afghanistan, killing three Afghan soldiers, a security official told the Associated Press.

The attackers slit the throats of the soldiers at the Sherabik post, near the Pakistani border, said Abdul Razzak Panjshiri, security chief in the Spin Boldak area. Five Taliban attackers were arrested, he said.

Weisman reported from Washington.

U.S. soldiers walked through Bagram air base, 35 miles north of Kabul, while 600 troops to the south searched for remnants of al Qaeda and the Taliban.