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Military groups expressed gratitude toward Afghan President Hamid Karzai on his visit Thursday to Arlington National Cemetery, where he paid his respects to fallen American troops.

Karzai and other VIPs walked Section 60 – what is frequently called the "saddest acre in America" – where troops killed in Afghanistan and other conflicts are laid to rest.

"As the mother of Sgt. Michael Carlson, who is buried in Section 60 at Arlington, I appreciate that the president of Afghanistan realizes, acknowledges and honors the sacrifice of the men and women who have died to bring peace and stability to Afghanistan," said Merrilee Carlson, a Goldstar mother and president of Military Families United.

"His trip demonstrates that he is aware that we are in this fight against terrorism, Al Qaeda and the Taliban forces together and that it is in the best interests of both America and the Afghani people that we continue to fight and build safety and security for them," she said in a written statement. "At the same time it is imperative that we must never forget the men and women who have made the ultimate sacrifice for our freedom and security."

Douglas McArthur, the executive director of the National Veterans Organization of America, described Karzai's visit as "noble."

"I think it was something that shows that he's appreciative of what the American soldiers buried there have done for his country," he told FoxNews.com.

Ami Neiberger-Miller, a spokeswoman for the Tragedy Assistance Program for Survivors, or TAPS, told FoxNews.com that Karzai's visit signaled that he cared and wanted to honor the fallen soldiers.

"The families I talked to have been touched that he was there ,and I think they've felt that it was appropriate for a head of state to go there," she said.

The father of one fallen U.S. soldier in Afghanistan, Lance Cpl. Timothy Poole Jr., 22, who was killed in January alongside two other Marines in a bomb blast, told Fox News that his family is still mourning the loss of his son.

"You don't want to know what it's like to stand at that Dover Air Force Base waiting for your son to fly home," Tim Poole Sr. said. "Watch them offload your son from the plane knowing you'll never see your son again, knowing you'll never hold your son again, you'll never hear your son say 'I love you.'"

Poole says his son wanted to be a Marine since he was 4 and told his father if he died it would be serving his country and doing what he wanted to do.

After spending some time with Karzai at Arlington Cemetery Thursday morning, the top commander for the war in Afghanistan, Gen. Stanley McChrystal spoke about the great sacrifice many American families are making there.

"Every single casualty affects people, it affects leaders, but more importantly, it affects families, it affects children, it affects parents, spouses," McChrystal said. "So each one of them is scared and I think we all know that."

McChrystal went on to say the force is strong but casualties are something he hopes the American people will keep in their minds and their hearts.

Editor's Note: Due to a reporting error, the original version of this article and a video that accompanied it mistakenly said that one of the graves President Karzai visited at Arlington was that of Lance Cpl. Timothy Poole Jr. In fact, Poole is buried at Jacksonville National Cemetery.

Fox News' Mike Emanuel and FoxNews.com's Stephen Clark contributed to this report.