WASHINGTON — The chairman of the Joint Chiefs of Staff says the insurgency in Afghanistan has grown for the past three years and that sending 30,000 U.S. troops in response is an attempt to blunt that momentum.

Navy Adm. Mike Mullen spoke to approximately 1,000 Marines at Camp Lejeune on Monday. Many of those who listened to his talk will be sent to Afghanistan as part of President Barack Obama's plan announced last week.

Camp Lejeune will supply 1,500 Marines by Christmas, Pentagon spokesman Bryan Whitman announced Monday. An additional 6,200 from Lejeune and Camp Pendleton in California are to follow by the end of spring.

The Lejeune Marines and sailors from II Marine Expeditionary Force are part of the first wave of about 16,000 U.S. troops to be deployed to the war zone

Mullen told the audience that military leaders believe they have between 18 and 24 months to reverse the insurgency or it might not be possible.

When asked by a Marine if he thought the boost of 30,000 additional troops was enough, he said, "Yes."

"You can't forget there are 42 other countries in Afghanistan with combat forces with us," Mullen said. "This isn't just the United States."

Earlier in the day, day, Mullen told soldiers at Fort Campbell, Ky., that he did expect casualties to rise next year.

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

Obama announced last week his plan to send 30,000 more troops to Afghanistan, saying the new policy was designed to "bring this war to a successful conclusion."

Mullen told troops their mission has two crucial elements: to ensure the safety of local civilians and to train Afghan security forces to take over as soon as possible.

The Lejeune Marines and sailors from II Marine Expeditionary Force are part of the first wave of about 16,000 U.S. troops to be deployed to the war zone

The group consists of Marines heading over for the first time, as well as those who have already been deployed to either Iraq or Afghanistan.

"I've been training pretty much my whole life for this, and a lot of the guys in my unit really wanted to get an opportunity to go over there and make a difference," Sgt. Derek MacPherson.

The Army will also begin sending in the first of its forces – a training brigade from Fort Drum, N.Y. Whitman said about 4,100 support forces from various places will also deploy early.

Among those units scheduled for deployment are:

• 2nd Marine Regiment Headquarters, 2nd Marine Division
• 1st Battalion, 2nd Marine Regiment, 2nd Marine Division
• 1st Battalion, 6th Marine Regiment, 2nd Marine Division
• 3rd Battalion, 6th Marine Regiment, 2nd Marine Division
• Company A, 2nd Light Armored Reconnaissance Battalion, 2nd Marine Division
• Company B, 2nd Assault Amphibian Battalion, 2nd Marine Division
• Company D, 2nd Tank Battalion, 2nd Marine Division
• Marine Heavy Helicopter Squadron 464, 2nd Marine Aircraft Wing
• 2nd Low Altitude Air Defense Battalion, 2nd Marine Aircraft Wing
• Combat Logistics Battalion 6, 2nd Marine Logistics Group
• Combat Logistics Company 16, 2nd Marine Logistics Group
• Detachment, II Marine Expeditionary Force Headquarters Group

The latest troop surge marks the second Obama has added to the American force in Afghanistan, where the Taliban has recently made significant advances.

When he became president last January, there were roughly 34,000 troops on the ground; there now are 71,000.

The United States went to war in Afghanistan shortly after the Sept. 11, 2001, al-Qaida terrorist attacks on the United States.

Osama bin Laden and key members of the terrorist organization were headquartered in Afghanistan at the time, taking advantage of sanctuary afforded by the Taliban government that ran the mountainous and isolated country.

Taliban forces were quickly driven from power, while bin Laden and his top deputies were believed to have fled through towering mountains into neighboring Pakistan.

While the al-Qaida leadership appears to be bottled up in Pakistan's largely ungoverned tribal regions, the U.S. military strategy of targeted missile attacks from unmanned drone aircraft has yet to flush bin Laden and his cohorts from hiding.

Defense Secretary Robert Gates has said that Americans should expect a significant U.S. military presence in Afghanistan for two years to four years more.

Just as in Iraq, the U.S. eventually will turn over provinces to local security forces, allowing the U.S. to bring the number of troops down steadily, according to Gates, who appeared on three Sunday talk shows with Secretary of State Hillary Rodham Clinton to discuss Obama's new Afghan war plan.