The nation's highest-ranking military officer Monday told soldiers, including many bound for Afghanistan, that he expects casualties to rise next year as additional U.S. troops pour into the war.

Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, answered soldiers' questions for about an hour at this sprawling Army post on the Kentucky-Tennessee line. Many at Fort Campbell already had orders for Afghanistan before President Barack Obama unveiled his plan last week to add about 30,000 new troops to about 70,000 already there.

"I am sure we will sustain an increase in the level of casualties and I don't want to be in any way unclear about that," he told about 700 troops. "This is what happened in Iraq during the surge and as tragic as it is, to turn this thing around, it will be a part of this surge as well."

"I expect a tough fight in 2010," Mullen said.

Mullen was due to talk later in the day at Camp Lejeune, N.C., the Marine Corps base that will supply about 1,500 Marines for the first surge units by Christmas.

After the first of the year, the Marines will begin sending another 6,200 from Lejeune and Camp Pendleton in California, the Pentagon announced Monday. The Army will also begin sending in the first of its forces in the spring _ a training brigade with about 3,400 soldiers from Fort Drum, N.Y. About 4,100 support forces from various places will also deploy early.

At Fort Campbell, Capt. Matthew O'Neill, 31, a member of the 101st Aviation Brigades, said he expects his scheduled deployment next year to Afghanistan may be sooner than expected as a result of the new strategy because ground troops rely on aviation units like his to move around the country.

"I just think the support that is needed in Afghanistan is finally getting put in," he said after Mullen's talk.

Many questions from soldiers focused on the role of Pakistan and America's NATO allies in containing al-Qaida and the Taliban.

Mullen said the border between Afghanistan and Pakistan is "the epicenter for global terrorism."

He said Pakistan's military has made huge gains in routing out terrorists from that country, but reminded soldiers that Pakistan is a sovereign nation and that the U.S. wants to maintain a long-term stable relationship with Pakistan.

"In the long run, we are anxious to get at al-Qaida and the leadership that resides in that border area," he said. "Strategically the way you do this in my view is to bring pressure from both sides."

Mullen, the president's senior military adviser, said Obama's announcement last week of a scheduled transition to a greater role for Afghan forces starting in July 2011 wasn't a deadline for pulling out troops.